@database "The Digital Universe Help File" @remark Copyright © 1995, Syzygy Research & Technology Ltd. All rights reserved. @node main "Main help index" This help file provides the on-line documentation necessary to use "The Digital Universe" successfully, and to fully understand the information it provides. The following categories of help are available: @remark beginverbatim @{"Starting The Digital Universe" link startdu} @{"Menus " link menus} @{"Windows " link windows} @{"Keyboard and Mouse Operations" link kbmouse} @{"Configuration of the software" link configuration} @{"Frequently Asked Questions " link faq} @{"Utilities " link utilities} @{"Product Information " link productinfo} @{"Ordering The Digital Universe" link ordering} @remark endverbatim @endnode @node menus "Menus" Help is available on the following menu items: @remark beginverbatim PROJECT: @{"About " link menu_about} -------------------- @{"Environment Prefs " link menu_environ} @{"Screenmode Prefs " link menu_screenmode} @{"Display/Object Prefs" link menu_display} @{"Fields of View " link menu_fields} @{"Open Control Panel " link menu_control} @{"Time Control " link menu_time} @{"Misc. Objects " link menu_miscobjs} -------------------- @{"Full sky view " link menu_fullsky} @{"Medium sky view " link menu_medsky} @{"Undo view " link menu_undo} @{"Redraw " link menu_redraw} @{"Recalculate " link menu_recalculate} -------------------- @{"Quit " link menu_quit} PRINT: @{"Full Screen " link menu_prfullscreen} @{"Full Page " link menu_prfullpage} MODE: @{"Planetarium " link menu_planetarium} @{"Local Sky " link menu_localsky} FIND: @{"Sun/Planet/Moon " link menu_findssystem} @{"Constellation " link menu_findconstellation} @{"Star " link menu_findstar} @{"Deep Sky Object " link menu_finddeepsky} @{"Misc. Object " link menu_findmiscobj} EXPORT: @{"Screen Snapshot " link menu_snapshot} @{"Animation " link menu_animation} @{"Reports " link menu_report} QUICKLOOK: @{"North " link menu_looknorth} @{"Northeast " link menu_looknortheast} @{"East " link menu_lookeast} @{"Southeast " link menu_looksoutheast} @{"South " link menu_looksouth} @{"Southwest " link menu_looksouthwest} @{"West " link menu_lookwest} @{"Northwest " link menu_looknorthwest} HELP: @{"Dictionary " link menu_dictionary} @{"Objects " link menu_objects} @{"People " link menu_people} @{"Spacecraft " link menu_spacecraft} -------------------- @{"Intro. to Astronomy " link menu_intro} -------------------- @{"Search Hypertext " link menu_searchht} @remark endverbatim @endnode @node menu_shortcut "Menu Shortcuts" Menu shortcuts are keys which may be pressed to access items from the menu without having to use the mouse. All shortcuts consist of pressing and holding the right "Amiga" key (immediately to the right of the spacebar) while pressing the shortcut key. For example, to choose "Environment Prefs" from the menu without using the mouse, press and hold the right "Amiga" key while typing "E". Menu shortcuts are indicated by a letter or character following a slanted, stylized "A" in the menu entry. @endnode @remark: Section describing various menu options @node menu_about "MENU:Project:About" @{"Menu Shortcut" link menu_shortcut} ? Choosing this option brings up the @{"About The Digital Universe" link window_about} window thanking the people who had various major roles in the development of the software. In addition, the window contains information on who the software is licensed to, as well as their registration number. @endnode @node menu_environ "MENU:Project:Environment Prefs" @{"Menu Shortcut" link menu_shortcut} E Choosing this option brings up the @{"Setting Environment Parameters" link window_environ} window, allowing you to change various factors about your physical environment; namely where you are on the Earth, the time zone you are in, and related information. @endnode @node menu_screenmode "MENU:Project:Screenmode Prefs" @{"Menu Shortcut" link menu_shortcut} S Choosing this option brings up the @{"Setting Screen Mode" link window_screenmode} window which allows you to change the screen resolution, monitor type, number of colors, etc. used by "The Digital Universe". @endnode @node menu_display "MENU:Project:Display/Object Prefs" @{"Menu Shortcut" link menu_shortcut} D Choosing this option brings up the @{"Display/Object Preferences" link window_display} window. This window allows you to customize a great variety of options used by "The Digital Universe" in generating a view on the screen (or printer - see @{"Full page" link menu_prfullpage} or @{"Full screen" link menu_prfullscreen} printing.) @endnode @node menu_fields "MENU:Project:Fields of View" @{"Menu Shortcut" link menu_shortcut} V Choosing this menu item brings up the @{"Field of View Preferences" link window_fields} window. This window allows you to set up to ten preset fields of view (in degrees), as well as a custom display orientation for each field. A simple keystroke will then zoom the display to one of the ten fields. @endnode @node menu_control "MENU:Project:Open Control Panel" @{"Menu Shortcut" link menu_shortcut} C Choosing this menu item brings up the @{"Control Panel" link window_control} window. This window allows you to pan around the simulated sky of "The Digital Universe", as well as quickly change various display options. @endnode @node menu_time "MENU:Project:Time Control" @{"Menu Shortcut" link menu_shortcut} T This option brings up the @{"Time Control" link window_time} window. This window allows you to set the current date and time used in the simulation of the sky, as well as specify the conditions of automatic or manual advancement through time. @endnode @node menu_miscobjs "MENU:Project:Misc. Objects" @{"Menu Shortcut" link menu_shortcut} O This menu item brings up the @{"Miscellaneous Objects" link window_miscobjs} window. This window allows you to specify which comets, asteroids, or Earth-orbiting satellites that "The Digital Universe" should consider. @endnode @node menu_fullsky "MENU:Project:Full Sky view" @{"Menu Shortcut" link menu_shortcut} F Picking this option from the menu zooms the display so that an entire hemisphere of the sky can be seen (180 degree field of view). Due to difficulties of displaying a round celestial sphere on a flat monitor, distortion will occur near the edges of the view. See also: @{"MENU:Project:Medium Sky view" link menu_medsky} @endnode @node menu_medsky "MENU:Project:Medium Sky view" @{"Menu Shortcut" link menu_shortcut} M Picking this menu option zooms the display so that a moderate field of view (70 degrees) is used. This can be useful to re-orient a user without causing severe distortions near the edges of the field. See also: @{"MENU:Project:Full Sky view" link menu_fullsky}. @endnode @node menu_undo "MENU:Project:Undo view" @{"Menu Shortcut" link menu_shortcut} U Choosing this option from the menu will "Undo" the last zoom and/or direction of view. "The Digital Universe" keeps track of your last ten views, and can therefore "undo" the display up to ten times. @endnode @node menu_redraw "MENU:Project:Redraw" @{"Menu Shortcut" link menu_shortcut} B Choosing "Redraw" from the Project menu will redraw the screen. This is useful if you have aborted a draw in progress and then later change your mind. Note that the Redraw option does only what it says - redraw the screen. If you aborted the generation of a display before the positions of various objects could be calculated, a redraw will not show them (since the computer has not calculated where they would appear). To recalculate their positions and redraw them on the screen, select @{"Recalculate" link menu_recalculate} from the Project menu instead. @endnode @node menu_recalculate "MENU:Project:Recalculate" @{"Menu Shortcut" link menu_shortcut} . Choosing "Recalculate" from the Project menu will recalculate the positions of objects and then redraw the screen. This is useful if you aborted a calculation in progress and then later change your mind. Note that the computer first determines where various objects will occur on the screen, and then draws them there. If you interrupted the computer while it was drawing objects on the screen, chances are that their positions had already been calculated. In such a situation, choosing @{"Redraw" link menu_redraw} from the Project menu would be much faster. @endnode @node menu_quit "MENU:Project:Quit" @{"Menu Shortcut" link menu_shortcut} Q Choosing this option from the Project menu will exit from "The Digital Universe". @endnode @node menu_prfullscreen "MENU:Print:Full Screen" @{"Menu Shortcut" link menu_shortcut} N If you pick this option from the "Print" menu, the software will attempt to print the contents of the current screen to your printer. "The Digital Universe" uses the configuration you have set up with your Workbench printer preferences. If you have not configured a printer for use with your Amiga, you must do so. Consult your Workbench documentation for more information. Print routines used with "The Digital Universe" make maximum use of the resolution of your printer. If you have a good quality printer and choose a density of 7 for your Workbench printer graphics preferences, the output will likely be superior to that on the screen. "Full Screen" printing means that the contents of the entire screen will be sent to the printer. Since a standard monitor is wider than it is high, but a piece of paper is higher than it is wide, the plot is scaled down so that it can fit horizontally across the paper. As a result, the lower portion of the paper will not be used. Landscape printing is not currently supported with "The Digital Universe". If you wish to fill an entire sheet of paper, use the @{"Full Page" link menu_prfullpage} mode. @{"View the difference between Full Page and Full Screen printing" system "execute showpic misc/printmodes.iff"} @endnode @node menu_prfullpage "MENU:Print:Full Page" @{"Menu Shortcut" link menu_shortcut} G If you pick this option from the "Print" menu, the software will attempt to print the contents of the current screen to your printer. "The Digital Universe" uses the configuration you have set up with your Workbench printer preferences. If you have not configured a printer for use with your Amiga, you must do so. Consult your Workbench documentation for more information. Print routines used with "The Digital Universe" make maximum use of the resolution of your printer. If you have a good quality printer and choose a density of 7 for your Workbench printer graphics preferences, the output will likely be superior to that on the screen. "Full Page" printing means that the plot will be scaled to fill the paper. Since a standard monitor is wider than it is high, but a piece of paper is higher than it is wide, the right and left edges of the image on the screen will not be appear on the paper. Landscape printing is not currently supported with "The Digital Universe". If you would rather print the entire contents of the screen, use the @{"Full Screen" link menu_prfullscreen} mode. @{"View the difference between Full Page and Full Screen printing" system "execute showpic misc/printmodes.iff"} @endnode @node menu_planetarium "MENU:Mode:Planetarium" @{"Menu Shortcut" link menu_shortcut} P If you put the software into "Planetarium" mode, it draws the screen so that celestial north is up. As a result, the horizon may not appear level. See also @{"Local Sky" link menu_localsky} mode. @endnode @node menu_localsky "MENU:Mode:Local Sky" @{"Menu Shortcut" link menu_shortcut} L If you put the software into "Local Sky" mode, it orients the screen so that it matches the view it would have from your position on the Earth. In this mode, the horizon appears to be level. See also @{"Planetarium" link menu_planetarium} mode. @endnode @node menu_findssystem "MENU:Find:Sun/Planet/Moon" @{"Menu Shortcut" link menu_shortcut} X Selecting this option from the "Find" menu brings up the @{"Sun, Planets, and Moons window" link window_findssystem}, allowing you to find the Sun, a planet, or a moon of interest. It is only enabled if you have set the option in the @{"Display/Object Preferences" link window_display} window to draw planets and their moons. @endnode @node menu_findconstellation "MENU:Find:Constellation" @{"Menu Shortcut" link menu_shortcut} Y Selecting this option brings up the @{"Constellation Selection" link window_findconstellation} window, allowing you to find a particular @{"constellation" link define.guide/constellation}. @endnode @node menu_findstar "MENU:Find:Star" @{"Menu Shortcut" link menu_shortcut} Z Selecting this option brings up the @{"Star Selection" link window_findstar} window, allowing you to find a particular star of interest. It is only enabled if you have set the option in the @{"Display/Object Preferences" link window_display} window to draw stars. @endnode @node menu_finddeepsky "MENU:Find:Deep Sky Object" @{"Menu Shortcut" link menu_shortcut} K Selecting this option brings up the @{"Deep Sky Object Selection" link window_finddeepsky} window, allowing you to find a @{"deep sky" link define.guide/deepsky} object of interest. It is only enabled if you have set the option in the @{"Display/Object Preferences" link window_display} window to draw deep sky objects. @endnode @node menu_findmiscobj "MENU:Find:Misc. Object" @{"Menu Shortcut" link menu_shortcut} J This menu option brings up the @{"Miscellaneous Object Selection" link window_findmiscobj} window, allowing you to find an @{"asteroid" link define.guide/asteroid}, @{"comet" link define.guide/comet}, or Earth-orbiting satellite of interest. It is only enabled if you have set the option in the @{"Display/Object Preferences" link window_display} window to draw miscellaneous objects. In addition, the only items which can be found are those which have been selected in the @{"Miscellaneous Objects" link window_miscobjs} window. @endnode @node menu_snapshot "MENU:Export:Screen Snapshot" @{"Menu Shortcut" link menu_shortcut} H The "Screen Snapshot" option allows you to take a "photograph" of the current screen. It brings up a file requester allowing you to specify a directory and filename into which it will save an IFF ILBM picture. By convention, IFF picture files should end in a .iff extension. IFF ILBM is the standard picture format for the Amiga, which can be viewed by a wide variety of software packages. The utility @{"showanim" link showanim} provided with "The Digital Universe" may also be used to view these pictures. An icon will be saved with the picture for Workbench users. It will use "showanim" to display the image. @endnode @node menu_animation "MENU:Export:Animation" @{"Menu Shortcut" link menu_shortcut} A Choosing this option from the "Export" menu will bring up the @{"Animation Control" link window_animation} window. From this window, you can create an unlimited variety of animation files, saved as an IFF ANIM. IFF ANIM is the standard animation format for the Amiga. A large selection of third party software packages can play animations in this format. The utility @{"showanim" link showanim} provided with "The Digital Universe" may also be used to view these animations. @endnode @node menu_report "MENU:Export:Reports" @{"Menu Shortcut" link menu_shortcut} R This menu option brings up the @{"Report Generation" link window_report} window, which allows you to output numerical reports to the printer or a file. @endnode @node menu_looknorth "MENU:Quicklook:North" @{"Menu Shortcut" link menu_shortcut} 8 Choosing this option will cause the software to generate a view of the sky as it appears to the north of your location. The menu shortcut for this option makes sense if you consider the numerical keypad to represent directions on a compass. @endnode @node menu_looknortheast "MENU:Quicklook:Northeast" @{"Menu Shortcut" link menu_shortcut} 9 Choosing this option will cause the software to generate a view of the sky as it appears to the northeast of your location. The menu shortcut for this option makes sense if you consider the numerical keypad to represent directions on a compass. @endnode @node menu_lookeast "MENU:Quicklook:East" @{"Menu Shortcut" link menu_shortcut} 6 Choosing this option will cause the software to generate a view of the sky as it appears to the east of your location. The menu shortcut for this option makes sense if you consider the numerical keypad to represent directions on a compass. @endnode @node menu_looksoutheast "MENU:Quicklook:Southeast" @{"Menu Shortcut" link menu_shortcut} 3 Choosing this option will cause the software to generate a view of the sky as it appears to the southeast of your location. The menu shortcut for this option makes sense if you consider the numerical keypad to represent directions on a compass. @endnode @node menu_looksouth "MENU:Quicklook:South" @{"Menu Shortcut" link menu_shortcut} 2 Choosing this option will cause the software to generate a view of the sky as it appears to the south of your location. The menu shortcut for this option makes sense if you consider the numerical keypad to represent directions on a compass. @endnode @node menu_looksouthwest "MENU:Quicklook:Southwest" @{"Menu Shortcut" link menu_shortcut} 1 Choosing this option will cause the software to generate a view of the sky as it appears to the southwest of your location. The menu shortcut for this option makes sense if you consider the numerical keypad to represent directions on a compass. @endnode @node menu_lookwest "MENU:Quicklook:West" @{"Menu Shortcut" link menu_shortcut} 4 Choosing this option will cause the software to generate a view of the sky as it appears to the west of your location. The menu shortcut for this option makes sense if you consider the numerical keypad to represent directions on a compass. @endnode @node menu_looknorthwest "MENU:Quicklook:Northwest" @{"Menu Shortcut" link menu_shortcut} 7 Choosing this option will cause the software to generate a view of the sky as it appears to the northwest of your location. The menu shortcut for this option makes sense if you consider the numerical keypad to represent directions on a compass. @endnode @node menu_dictionary "MENU:Help:Dictionary" @{"Menu Shortcut" link menu_shortcut} None Selecting this menu item will bring up a @{"hypertext" link define.guide/hypertext} dictionary of astronomy and computer-related terms. @{"Link to dictionary" link define.guide/main} @endnode @node menu_objects "MENU:Help:Objects" @{"Menu Shortcut" link menu_shortcut} None Selecting this menu item will bring up a @{"hypertext" link define.guide/hypertext} guide to a vast amount of information about various objects in the solar system and elsewhere, organized as a multimedia-based encyclopedia. @{"Link to object descriptions" link duobjects.guide/main} @endnode @node menu_people "MENU:Help:People" @{"Menu Shortcut" link menu_shortcut} None Selecting this menu item will bring up a @{"hypertext" link define.guide/hypertext} guide to a number of prominent individuals in astronomy. @{"Link directly to information about individuals" link people.guide/main} @endnode @node menu_spacecraft "MENU:Help:Spacecraft" @{"Menu Shortcut" link menu_shortcut} None This menu item will bring up a @{"hypertext" link define.guide/hypertext} multimedia encyclopedia of all interplanetary spacecraft as well as several Earth-orbiting satellites. @{"Link to Spacecraft Encyclopedia" link spacecraft.guide/main} @endnode @node menu_intro "MENU:Help:Intro. to Astronomy" @{"Menu Shortcut" link menu_shortcut} I Choosing this item will bring up a @{"hypertext" link define.guide/hypertext} multimedia encyclopedia providing an introduction to astronomy. @{"Link to Introduction to Astronomy" link astro.guide/main} @endnode @node menu_searchht "MENU:Help:Search Hypertext" @{"Menu Shortcut" link menu_shortcut} W Selecting this item from the menu will bring up the @{"Search Hypertext Files" link window_searchht} window. This window will allow you to search through all the help files looking for a word or phrase. @endnode @remark: Section describing various windows @node windows "Windows" Context-sensitive help is available by simply pressing the HELP key when the mouse pointer is over the window or @{"gadget" link define.guide/gadget} you wish to have explained. As a result, help for a particular window is not usually obtained by going through this menu, but it is provided for users that make their way here one way or another. @remark beginverbatim @{"About The Digital Universe " link window_about} @{"Setting Environment Parameters " link window_environ} @{"Setting Screen Mode " link window_screenmode} @{"Display/Object Preferences " link window_display} @{"Field of View Preferences " link window_fields} @{"Control Panel " link window_control} @{"Time control " link window_time} @{"Miscellaneous Objects " link window_miscobjs} @{"Sun, Planets, and Moons " link window_findssystem} @{"Constellation Selection " link window_findconstellation} @{"Star Selection " link window_findstar} @{"Deep Sky Object Selection " link window_finddeepsky} @{"Miscellaneous Object Selection " link window_findmiscobj} @{"Animation Control " link window_animation} @{"Report Generation " link window_report} @{"Search Hypertext Files " link window_searchht} @{"Printing Status " link window_printing} @{"Object Information " link window_objectinfo} @{"Multiple Objects " link window_multiobject} @{"Calculating... " link window_calculating} @{"Miscellaneous Object Orbit Entry" link window_editobject} @remark endverbatim @endnode @node window_multiobject "Multiple Objects Window" Normally, when you click the mouse pointer on an object on the screen, a window appears giving detailed information about the object. However, if more than one object is under the pointer, "The Digital Universe" needs to know which object you want more information about. To find out, it brings up the Multiple Object Selection Window, containing a list of objects sorted by increasing @{"magnitude" link define.guide/magnitude} (brighter objects at the top of the list). For objects with multiple names or designations, such as the brighter stars, only the most commonly used name is displayed. The designation for the object is shown on the left, and its magnitude is on the right. To choose which object you are interested in, simply click on it. Detailed information will then appear. If you change your mind and would rather not obtain further information about anything, just close the window. @endnode @node window_about "About The Digital Universe Window" This window lists several of the people who have had important roles in the development of "The Digital Universe". In addition, this window contains information about who the software is registered to, as well as their registration number. Please use this registration number in any correspondence you may have with us. Our postal address is: Syzygy Research & Technology Ltd. Box 75 Legal, AB T0G 1L0 CANADA In addition, you can contact us by sending Internet email to sales@syz.com or support@syz.com. You can also visit our World Wide Web (WWW) site with the following URL: http://www.syz.com @endnode @node window_environ "Setting Environment Parameters" This window allows you to change various factors about your physical environment, such as your location on the Earth, the time zone you are in, etc. For more information on a particular @{"gadget" link define.guide/gadget}, place your mouse pointer over the gadget of interest and press the HELP key. Note that to make changes in this window take effect, you must press the @{"Save" link environ_save} or @{"Use" link environ_use} button at the bottom of the window. If you simply close the window, the software will use your old environment configuration. Further help is available for the following gadgets in this window: @remark beginverbatim @{"Latitude " link environ_latitude} @{"Longitude " link environ_longitude} @{"Altitude " link environ_altitude} @{"Temperature " link environ_temperature} @{"Pressure " link environ_pressure} @{"City List " link environ_cities} @{"Current City " link environ_currentcity} @{"Time Zones " link environ_timezones} @{"Current Time Zone" link environ_currenttimezone} @{"Time Zone Offset " link environ_offset} @{"Load " link environ_load} @{"Save " link environ_save} @{"Use " link environ_use} @{"Horizon File " link environ_horizonfile} @remark endverbatim @endnode @node environ_latitude "Latitude" There are two methods of telling "The Digital Universe" where you are. One is to simply click on a nearby city in the @{"list" link environ_cities}. The other is to directly enter your position. This box allows you to specify your latitude, if you would rather enter your location manually than click on a city in the list below this gadget. The latitude must be of the format "DD:MM:SSX" where: DD = degrees MM = minutes SS = seconds X = `S' or `N' (South or North) For an example of acceptable format, click on a city in the list below. If you prefer, your latitude may also be entered in decimal degrees, followed by `N' or `S', as before. @endnode @node environ_longitude "Longitude" There are two methods of telling "The Digital Universe" where you are. One is to simply click on a nearby city in the @{"list" link environ_cities} below. The other is to directly enter your position. This box allows you to specify your longitude, if you would rather enter your location manually than click on a city in the list below this gadget. The longitude must be of the format "DDD:MM:SSX" where: DDD = degrees MM = minutes SS = seconds X = `E' or `W' (East or West) If you prefer, your longitude may also be entered in decimal degrees, followed by `E' or `W', as before. @endnode @node environ_altitude "Altitude" Since "The Digital Universe" is capable of generating the appearance of the night sky to a great deal of precision, serious observers will want to take advantage of the fact that the software can make adjustments depending on your altitude above sea level. If you know your altitude, you may enter it in this box. Your altitude should be entered in a form similar to `1000m' or `1000f' for 1000 metres or 1000 feet above sea level, respectively. If you leave the box empty, the software will assume a default altitude equal to sea level. @endnode @node environ_temperature "Temperature" If "The Digital Universe" is configured to take @{"refraction" link define.guide/refraction} into account when determining the position of stars and other objects, it needs to know the approximate temperature. This is because colder air bends light more strongly than warm air. By entering the current temperature into this box, the software will make the appropriate adjustments. This ability is only of limited use, however, since the true apparent position of an object depends on the temperature and pressure at different atmospheric levels - not just the conditions on the ground. A valid entry for temperature should be similar to: 20C or 70F or 300K to represent degrees Celsius, Fahrenheit, or @{"Kelvin" link define.guide/kelvin}, respectively. In addition, the given temperature should be between -100 to 100 degrees Celsius, -148 to 212 degrees Fahrenheit, or 173 to 373 Kelvin. @endnode @node environ_pressure "Pressure" If "The Digital Universe" is configured to take @{"refraction" link define.guide/refraction} into account when determining the position of stars and other objects, it needs to know the approximate pressure. This is because high pressure air bends light more strongly than that of low pressure. By entering the current pressure into this box, the software will make the appropriate adjustments. This ability is only of limited use, however, since the true apparent position of an object depends on the temperature and pressure at different atmospheric levels - not just the conditions on the ground. A valid entry for pressure should be similar to: 101K or 29.9I to represent 101 kilopascals (kPa) or 29.9 inches of mercury, respectively. The given pressure should be between 0 to 200 kPa or 0 to 59 inches of mercury. @endnode @node environ_cities "Cities and towns" "The Digital Universe" contains a database of the locations of 1230 different cities and towns worldwide. If one of the entries is near where you live, all you have to do is click on it. Then, the latitude, longitude, and altitude (if known) of this location will be entered automatically in the appropriate boxes above. It should be remembered that cities and towns take up a certain amount of size on the Earth's surface. The coordinates provided by the internal database usually refer to the geographical center of the settlement. If a high degree of accuracy is required, you may need to adjust the location manually to your observing location. "The Digital Universe" is accurate enough that an error of only a few hundred metres (a few arcseconds) in latitude and longitude can make a detectable difference. There are two `special' locations in this list. should be used when specifying a location not otherwise in the list. `Geocentric location' places you at the centre of the Earth. Many tables and almanacs tabulate events as they occur from a @{"geocentric" link define.guide/geocentric} position, so the ability to define your location as such is useful in comparing the calculations of "The Digital Universe" to published values. @endnode @node environ_timezones "Time Zones" The world is divided up into several different time zones. "The Digital Universe" needs to know which time zone you are in so that it can use your own local time in simulating the appearance of the sky. Time zones can be specified by two different methods: by name, and by the number of hours it is kept away from Greenwich Mean Time (also known as Universal Time - UT). If you see your time zone in the list, a simple click on it will enable the software to calculate the offset from UT. If your time zone is not listed, select at the top of the list, and then enter the appropriate value into the @{"Offset" link environ_offset} requester. Some places in the world make use of something known as "Daylight Savings Time". Regions with this policy usually set clocks an hour ahead in the spring, and an hour behind in the fall. Since the dates at which Daylight Savings Time occurs vary from region to region (based on local custom and politics), "The Digital Universe" is unable to determine on its own when to consider Daylight Savings Time. This means that twice per year you may have to change your time zone entry. Most zones appear twice in the list - once as a "Standard" time, and once as a "Daylight" time. For example, you may have to change your time zone from "Mountain Standard Time" in the winter to "Mountain Daylight Time" in the summer. @endnode @node environ_currenttimezone "Current Time Zone" This little box indicates which time zone is currently being used by the software. @endnode @node environ_currentcity "Current City" This box indicates which city has been selected in the @{"list" link environ_cities} above. @endnode @node environ_offset "Time Zone Offset" This indicates the current time zone offset from Universal Time (UT). It is expressed in hours and minutes (in the form +HH:MM or -HH:MM), and is calculated by subtracting the current Universal Time from the current Local Time. As a result, time zones in the western hemisphere are usually expressed as negative offsets, while time zones in the eastern hemisphere are positive. You can only enter a value into this box if you have selected from the @{"time zone list" link environ_timezones} above. @endnode @node environ_load "Load" This button allows you to load a preset environment configuration. If selected, a file requester is brought up allowing you to specify the file from which to load the configuration. As a standard, environment filenames should end with an ".environ" extension. When the program first starts, it attempts to read the default environment from a file named "du.environ". By allowing multiple configurations in this manner, "The Digital Universe" allows you to preset the environment settings for every observing site you have. @endnode @node environ_save "Save" This button allows you to save an environment configuration. If selected, a file requester is brought up allowing you to specify the file in which to save the configuration. Environment filenames should end with an ".environ" extension. If you save the configuration as a file named "du.environ", the settings will be loaded every time the program is started. By allowing multiple configurations in this manner, "The Digital Universe" allows you to preset the environment settings for every observing site you have. If you have entered invalid data somewhere on the window, the program will not let you save your configuration. Instead, it will describe what the problem is and give you the chance to fix it. @endnode @node environ_use "Use" This button allows you to use the environment settings specified in the window. These settings will only be used for the current session with the software - if you wish to make them permanent, press the @{"Save" link environ_save} button instead. If you have entered invalid data somewhere on the window, the program will not let you use your configuration. Instead, it will describe what the problem is and give you the chance to fix it. @endnode @node environ_horizonfile "Horizon File" "The Digital Universe" is capable of drawing more than just a simple line to represent your horizon. Since few of us have truly flat horizons, the software will allow you to specify a special file describing its appearance. By convention, horizon filenames should end in the ".hor" extension. You may enter the filename (complete with path) into the box provided. If preferred, you can click on the image to the right of the input box to bring up a file requester to choose the file. Note that a horizon is only drawn if the appropriate option is selected in the @{"Display/Object Preferences" link window_display} window. A sample horizon file, named "sample.hor", is provided with "The Digital Universe". For more information, see @{"The Horizon File Format" link horizonfileformat}. @endnode @node horizonfileformat "The Horizon File Format" If you have instructed the software to draw a horizon, through enabling the appropriate option in the @{"Display/Object Preferences" link window_display} window, it will, by default, draw a straight horizontal line. However, few of us have truly flat horizons. Therefore, "The Digital Universe" will draw a customized horizon if you ask it to. This is done by specifying the "horizon file" from the @{"Setting Environment Parameters" link window_environ} window. A horizon file can be created by any word processor or text editor capable of generating plain ASCII output. It should consist of 360 lines, with a single decimal number on each line. Line number `n' will contain the @{"altitude" link define.guide/altitude} of the horizon, in degrees, for the @{"azimuth" link define.guide/azimuth} of (n-1) degrees. In other words, the first line should contain the altitude of your horizon straight north (at an azimuth of 0 degrees). The next line should contain the altitude of your horizon 1 degree to the east of that, and so on for 360 degrees. Of course, it could get rather tedious obtaining and entering 360 different altitude measurements. The software requires the altitude of the horizon directly north (as the first line), but will interpolate for any other intermediate values if you give them an altitude of 100. Thus, you can create a less detailed horizon file by only specifying the coordinates you want (including the point on the horizon to the north), and entering 100 for every other line. When creating a horizon file, it may be easiest to modify a copy of "sample.hor", provided as an example with "The Digital Universe". Determining Altitude/Azimuth Measurements for your Horizon ========================================================== Since not many people have access to a theodolite or professional surveying instrument, a method is described here to obtain rough measurements of the altitude of your horizon at varying degrees of azimuth. You must first find the point on your horizon due north of your observing location. Northern hemisphere observers can approximate this on a clear night by finding @{"Polaris" link duobjects.guide/object000001A8}, the North Star. If you hang a weight from a string and line it up so it appears to pass over Polaris, it will intersect the horizon at a position within a degree or so of true north. Since southern hemisphere observers cannot view Polaris, and do not have an equivalent bright "South Star", they must find true north by getting "The Digital Universe" to find the time when any bright star lies directly to the north of their location. This is done by finding a bright star lying north of the @{"celestial equator" link define.guide/celestialequator} (having a positive @{"declination" link define.guide/declination}), and clicking on it to find its local time of @{"meridian" link define.guide/meridian} @{"transit" link define.guide/transit}. This star can then be used in place of Polaris, but only at the specified time. Remember where this north point is located, and come back out to your observing site in the day, bringing a protractor, level, and a ruler with you. If you line the protractor so that 0 degrees points directly north and the numbers increase in a clockwise direction, they will indicate azimuth angles. To take an altitude measurement at a particular azimuth, point the level in the proper azimuth direction, and keep it level. Put your eye at one end of the level, and adjust the ruler at the other end until the tip of it appears to line up with the horizon. Read off the distance between the tip of the ruler and the top of the level, then divide this number by the length of the level. If you then use a scientific calculator to determine the arctangent of the result, you are left with the altitude of your horizon. @{"View diagram of how to measure altitude" system "execute showpic misc/horizonmeasure.iff"} @endnode @node window_screenmode "Setting Screen Mode Window" This window allows you to change the screen resolution, monitor type, number of colors, etc. used by "The Digital Universe". For more information on a particular @{"gadget" link define.guide/gadget}, place your mouse pointer over the gadget of interest and press the HELP key. Note that to make changes in this window take effect, you must press the @{"Save" link screen_save} or @{"Use" link screen_use} button at the bottom of the window. If you simply close the window, the software will use your old screenmode configuration. Help is available for the following gadgets: @remark beginverbatim @{"Screen list " link screen_screens} @{"Current screen" link screen_current} @{"Use topaz font" link screen_usetopaz} @{"Screen size " link screen_size} @{"# of colors " link screen_colors} @{"Save " link screen_save} @{"Use " link screen_use} @remark endverbatim @endnode @node screen_screens "List of Screens" This list shows the different screenmodes which your Amiga is capable of using. You can choose any mode by simply clicking the mouse pointer on it. The @{"Save" link screen_save} or @{"Use" link screen_use} button must then be selected for the changes to take effect. The first entry in the list is labeled . If this is selected, "The Digital Universe" will open up an NTSC Hires Interlaced screen if you are using an NTSC monitor, or a PAL Hires Interlaced screen if you are using a PAL monitor. @endnode @node screen_current "Current Screen" This box shows the screenmode which you have selected in the list of screens above. Remember that "The Digital Universe" will not use the selected screenmode unless you click on the @{"Save" link screen_save} or @{"Use" link screen_use} buttons below. @endnode @node screen_usetopaz "Use Topaz font" If you have selected a non-interlaced screen in the @{"screenmode list" link screen_screens} and are using a font other than Topaz/8 as your default system font, some of the windows used with "The Digital Universe" may become too large to display. If this happens, the window will simply not appear on the screen when it should. If you tell the software to use the topaz font, it will override your system default preferences so that all the windows can be displayed. If you are running a screen with more than 200 lines of vertical resolution, you will probably not need to select this @{"gadget" link define.guide/gadget}. @endnode @node screen_size "Screen Width and Height" You can enter your desired screen width and height into these boxes (in pixels). If you select a screenmode from the list to the left, the default sizes will appear. However, if you wish to use a "virtual" screen larger in size, simply increase the number in this box. If you choose a screen size larger than that which can be shown on your monitor, you can scroll about simply by moving your mouse to the edges of the display. In this way, the size of the screen you wish "The Digital Universe" to use is limited only by the amount of chip (graphics) memory you have, and not by the capabilities of your monitor. If you increase the screen dimensions to a size which cannot be supported by the amount of chip memory that you have, the software will reduce the screen until it fits. Note that the size chosen by "The Digital Universe" may not necessarily be the largest screen which can fit with the memory that you have, but will be a bit smaller. If "The Digital Universe" opens up a screen smaller than that which you know you have been able to use in the past, chances are that your chip memory has become fragmented. Usually, rebooting the computer will solve the problem. @endnode @node screen_colors "Number of colors" This slider allows you to change the number of colors used by "The Digital Universe". The software currently only uses screens of 8 or 16 colors. If 8 colors are chosen, everything appears on the screen as varying shades of gray. If 16 colors are chosen, color is used for the purposes of labeling, drawing grid lines, etc. However, 33% more chip memory is required. @endnode @node screen_save "Save" If you press this button, the preferences you have set for your screenmode are saved to the configuration file used by the software when it is started. In this way, your changes are made permanent, and it will use these preferences every time you use "The Digital Universe" in the future. If you wish to use your preferences for the current session only, click on the @{"Use" link screen_use} button instead. @endnode @node screen_use "Use" The "Use" button tells "The Digital Universe" to use the preferences for screenmode and number of colors that you have set up. These preferences are only active for your current session - the next time you use the software, it will use its old settings. If you wish to save the settings for future use, press the @{"Save" link screen_save} button instead. Then, your settings will be in effect every time the software is loaded. @endnode @node window_display "Display/Object Preferences Window" This window allows you to customize a great variety of options used by "The Digital Universe" in generating a view on the screen (or printer - see @{"Full page" link menu_prfullpage} or @{"Full screen" link menu_prfullscreen} printing.) For more information on a particular @{"gadget" link define.guide/gadget}, place your mouse pointer over the gadget of interest and press the HELP key. Note that to make changes in this window take effect, you must press the @{"Save" link display_save} or @{"Use" link display_use} button at the bottom of the window. If you simply close the window, the software will use your old display configuration. Help is available for the following gadgets: @remark beginverbatim Calculation & Display ===================== Display ------- @{"Ra/dec grid " link display_radec} @{"Horizon " link display_horizon} @{"Fast Labels " link display_fastlabels} @{"Fast info " link display_fastinfo} @{"Show Time " link display_time} @{"Flip Horizontal " link display_flip} @{"Flip Vertical " link display_flip} @{"Star trails " link display_startrails} @{"Show FOV " link display_fov} @{"Show Titlebar " link display_title} @{"Earth's Shadow " link display_shadow} Precision --------- @{"Precession " link display_precession} @{"Proper Motion " link display_propermotion} @{"Nutation " link display_nutation} @{"Aberration " link display_aberration} @{"Refraction " link display_refraction} Objects ------- @{"Stars " link display_stars} @{"Sun/Planet/Moon " link display_ssystem} @{"Deep Sky " link display_galaxy} @{"Misc. Object " link display_miscobject} Palette ------- @{"Use night palette " link display_night} @{"Simulate Twilight " link display_twilight} Object Preferences ================== Stars ----- @{"Bayer Designation " link display_bayer} @{"Flamsteed number " link display_flamsteed} @{"Star names " link display_starnames} Deep Sky -------- @{"NGC/IC # " link display_ngc} @{"Messier # " link display_messier} @{"Names " link display_deepskynames} Sun, Planets & Moons -------------------- @{"Show Phase " link display_phase} @{"Features & Flattening" link display_features} @{"Show Grid " link display_planetgrid} @{"Object Names " link display_planetnames} Miscellaneous Objects --------------------- @{"Misc. Object Names " link display_miscobjectnames} Constellations -------------- @{"Boundaries " link display_boundaries} @{"Figures " link display_figures} @{"Names " link display_names} Limiting Magnitudes =================== @{"Stars/Planets " link display_limmag} @{"Deep Sky " link display_ngclimmag} @{"Misc. Object " link display_misclimmag} @{"Save " link display_save} @{"Use " link display_use} @endnode @node display_radec "RA/Dec grid" Selecting this option causes the software to draw the grid lines of @{"right ascension" link define.guide/rightascension} and @{"declination" link define.guide/declination} on the screen. @endnode @node display_horizon "Horizon" If this option is selected, "The Digital Universe" will draw the horizon on the screen. If no @{"horizon file" link environ_horizonfile} has been chosen in the @{"Setting Environment Parameters" link window_environ} window, just a simple line will be drawn, representing an ideal, flat horizon. On the other hand, if a horizon file has been selected, a representation of the user's horizon will be generated as well. Note that the horizon will only appear level if the software is in @{"Local Mode" link menu_localsky}. @endnode @node display_fastlabels "Fast Labels" When "The Digital Universe" labels stars, planets, or other objects, it can do so by one of two methods: @remark beginverbatim 1. The label is just placed to the right of the object. 2. The label's position is adjusted so as to minimize overlap with nearby labels and objects. @remark endverbatim The "Fast Labels" @{"gadget" link define.guide/gadget} allows you to choose which method to use. If it is selected, labels are placed to the right of the object. This is much faster than the second method, though the results do not look as good. @endnode @node display_fastinfo "Fast Info" If you click the mouse pointer on an object on the screen, a window is displayed containing information about it. For objects which move with respect to the background stars (such as planets), information such as rise and set times is difficult to determine and may take some time to calculate. If this @{"gadget" link define.guide/gadget} is selected, these calculations will not be performed, speeding up the process of obtaining information about an object. In such a case, the affected information will be marked "Unavailable". @endnode @node display_time "Show Time" If this option is selected, the time used by the software in performing its calculations is displayed in the upper left hand corner of the screen (or paper, if a printed copy is made). Two times are displayed: LT (Local Time) and DT (@{"Dynamical Time" link astro.guide/dynamicaltime}). @endnode @node display_flip "Flip Horizontal and/or Vertical" If you have a telescope, the apparent view through it may be flipped in the horizontal and/or vertical axes. These buttons allow you to specify whether you want "The Digital Universe" to produce such an inverted image to match that seen through your telescope. @endnode @node display_startrails "Star trails" Normally, when the software steps through time (either automatically, manually, or when generating an animation), it erases the screen before redrawing the new image. If this option is selected, however, the screen will not be erased. This allows you to generate views showing how objects move across the sky, which appear similar to "star trail" photographs made by leaving a camera's shutter open for long periods of time. @endnode @node display_fov "Show FOV" The "field of view" indicates how much of the sky you can see at once. It can be thought of as a circular region with a particular angular diameter. With smaller fields of view, objects appear larger on the screen, but fewer objects can be seen at once. Since a "field of view" is really a circular region, but computer monitors are rectangular in shape, "The Digital Universe" adjusts the display so that the field will just fit vertically on the monitor. If you choose the "Show FOV" option, a circle will be drawn indicating the true field of view on the display. @endnode @node display_title "Show Titlebar" Most Amiga programs have a title bar at the top of their screen. However, users of "The Digital Universe" may find its title bar distracting when viewing dim stars. Thus, the user is provided with the option of disabling the title bar, if desired. Note that if the title bar is disabled, the user will be unable to use the regular screen rearrangement gadgets normally appearing within it. @endnode @node display_shadow "Earth's Shadow" The Sun casts a shadow of the Earth into space. Objects near to the Earth (such as Earth-orbiting satellites and the Moon) may periodically move into this shadow and drastically darken in appearance. When the Moon moves into the Earth's shadow, a @{"lunar eclipse" link define.guide/lunareclipse} occurs. If this @{"gadget" link define.guide/gadget} is selected, "The Digital Universe" draws a representation of the Earth's shadow as it appears at the distance of the Moon. The outer circle drawn shows the region of the @{"penumbral" link define.guide/penumbra} shadow, while the inner circle indicates the region of the @{"umbra" link define.guide/umbra}. By telling the software to draw the Earth's shadow, the circumstances of lunar eclipses can be readily determined. @endnode @node display_stars "Stars" If this option is selected, stars will be drawn on the screen when the software is generating a view of the sky. For normal use this should be left on. However, if turned off, the display is updated much more quickly. The difference is especially noticeable when generating a view of the sky for the far past or future. For example, if you are generating an animation of the appearance of Saturn and its rings, you will likely be zoomed in so closely to the planet that you wouldn't see the stars anyway. Turning them off would allow the animation to proceed much more quickly. @endnode @node display_ssystem "Sun/Planet/Moon" This @{"gadget" link define.guide/gadget} allows you to specify whether or not you want "The Digital Universe" to calculate the positions of the Sun, planets, and their moons. Though it should be left on for an accurate representation of the night sky, there are many cases where an individual merely wishes to study the stars. On machines without a math coprocessor (FPU), updates to the display are much faster if the software doesn't have to calculate the position of these objects. @endnode @node display_galaxy "Deep Sky Objects" If this option is selected, the software will determine and plot the position of @{"deep sky" link define.guide/deepsky} objects from the Messier, NGC, and IC databases. Since doing so can slow the display, the user is provided with the ability to turn the feature on or off. @endnode @node display_miscobject "Miscellaneous Objects" If this option is selected, "The Digital Universe" will calculate and plot the positions of any miscellaneous objects (@{"comets" link define.guide/comet}, @{"asteroids" link define.guide/asteroid}, Earth-orbiting satellites, etc.) which you have selected in the @{"Miscellaneous Objects" link window_miscobjs} window. @endnode @node display_precession "Precession" Choosing this option allows the software to calculate the effects of @{"precession" link define.guide/precession} when determining the appearance of the sky. It slows down calculations significantly, so should only be chosen when you want high accuracy, or are simulating the sky for dates in the far future or past. If selected, celestial objects are precessed to the @{"epoch" link define.guide/epoch} defined in the @{"Time Control" link window_time} window. @endnode @node display_propermotion "Proper Motion" If this option is selected, the software will consider @{"proper motion" link define.guide/propermotion} of the stars in determining their positions. Since proper motion calculations slow the software down somewhat, and it is only a significant effect over time periods of thousands of years, it can often be disabled. If this option is selected, the effect of proper motion is applied to adjust the star's position to where it would be at the @{"epoch" link define.guide/epoch} defined in the @{"Time Control" link window_time} window. @endnode @node display_nutation "Nutation" If this option is selected, the software will consider the effects of @{"nutation" link define.guide/nutation}. Nutation is typically a small effect, noticeable only when zoomed in to a small region of the sky. Therefore, unless high accuracy is desired, it can often be left disabled to speed calculations. @endnode @node display_aberration "Aberration" If this @{"gadget" link define.guide/gadget} is selected, the effects of @{"aberration" link define.guide/aberration} will be considered in generating a simulated view of the sky. Aberration is only noticeable when zoomed in to a particularly small region of sky, and can therefore often be left disabled, speeding calculations. @endnode @node display_refraction "Refraction" @{"Refraction" link define.guide/refraction} will be considered when generating views of the sky if this option is selected. If you are interested only in the relative positions of nearby objects, you can speed up calculations by leaving this @{"gadget" link define.guide/gadget} unselected. This is because refraction affects objects in the same part of the sky by the same amounts. However, if you are interested in the apparent position of objects near the horizon, refraction can affect their position by a half a degree or so, so it may be significant. If refraction is turned on, and you zoom in to the Sun or Moon as they rise or set, you will be able to see how refraction makes their appearance seem "squashed" when near the horizon. Refraction calculations use the current temperature and air pressure as set in the @{"Setting Environment Parameters" link window_environ} window to provide a reasonably accurate estimate of the effect. @endnode @node display_night "Use Night Palette" When you look at the night sky, it takes a half hour or more for your eyes to get as sensitive to light as they are capable of becoming. This "dark adaptation" is necessary for seeing the fainter objects in the sky. However, a light source is sometimes needed to be able to look at star charts, equipment, etc. in the dark. A bright white light from a flashlight ruins your dark adaptation, and some time is required before your eyes get used to the dark once again. Scientists have discovered that red light does not affect our eye's sensitivity nearly as much as white light. Therefore, astronomers often use flashlights with a red filter over the front of them to preserve their dark adaptation. Computer monitors are notoriously bad for affecting night vision. With this in mind, "The Digital Universe" provides a special night palette for those observers who may be using their computer near the telescope. When selected, this @{"gadget" link define.guide/gadget} uses a special black and red palette instead of the standard one. @endnode @node display_twilight "Simulate Twilight" Normally, the software shows the stars even if the Sun is in the sky. This allows users to study celestial objects and events without having to worry about the constraint of the Sun being below the horizon. This is quite useful, if a bit unrealistic. If this @{"gadget" link define.guide/gadget} is selected and the Sun is currently in the sky, the background changes from black to blue, with only the brightest objects remaining visible. After sunset, the background slowly changes from blue to black, simulating the effect of twilight. Throughout the night, the sky remains black, slowly fading to blue again before dawn. This gadget can only be selected if the software is set up to calculate the position of planets and their moons by enabling the @{"Sun/Planet/Moon" link display_ssystem} option. If it is not, the position of the Sun is unknown and twilight cannot be simulated. @endnode @node display_boundaries "Constellation Boundaries" @{"Constellations" link define.guide/constellation} have been defined in the heavens for thousands of years. But these constellations have only consisted of a few stars linked together into shapes. In 1930, E. Delaporte realized that it would be useful to define particular constellations on the basis of the regions in the sky which they occupy, instead of just a few stars making up the figure. He published a list of proposed constellation boundaries in a work entitled "Délimitation Scientifique des Constellations", which soon became accepted by the astronomical community. Selecting this @{"gadget" link define.guide/gadget} displays the constellation boundaries as outlined by Delaporte. His boundaries fall directly on lines of constant @{"right ascension" link define.guide/rightascension} and @{"declination" link define.guide/declination} when 1875 coordinates are used (the standard at the time of his publication). Since then, however, @{"precession" link define.guide/precession} has caused the boundaries to shift slightly, so they do not always seem to line up perfectly. @endnode @node display_figures "Constellation Figures" Selecting this option causes the software to connect the stars into various @{"constellation" link define.guide/constellation} figures. As of version 1.01 of "The Digital Universe", constellation figures will follow the stars in @{"proper motion" link define.guide/propermotion} calculations. As a result, it may take a short time to draw constellation figures if proper motion is selected in the @{"Display/Object Prefs" link window_display} window. @endnode @node display_names "Constellation Names" If this option is selected, @{"constellation" link define.guide/constellation} names will appear on the screen. An interesting detail can be seen with the constellation of "Serpens" (the serpent). Since it is considered to be held by "Ophiuchus" (the serpent holder), the two constellations actually overlap one another. This caused some problems when trying to divide the sky into regions, delineated by constellation boundaries. As a result, some astronomers subdivide Serpens into two smaller constellations - "Serpens Caput" (the serpent's head) and "Serpens Cauda" (the serpent's tail). The region of Serpens directly overlapping Ophiuchus is considered to be part of the latter constellation. @endnode @node display_ngc "NGC/IC #" If this option is selected, "The Digital Universe" will label any @{"deep sky" link define.guide/deepsky} object with its @{"NGC" link define.guide/ngc} or @{"IC" link define.guide/ic} numbers. It can only be selected if the software is configured to display deep sky objects. @endnode @node display_messier "Messier #" If this @{"gadget" link define.guide/gadget} is selected, the software will label any @{"Messier" link define.guide/messier} objects which may appear on the screen. It can only be selected if the software is configured to display @{"deep sky" link define.guide/deepsky} objects. @endnode @node display_deepskynames "Names" If this option is selected, the software will label @{"deep sky" link define.guide/deepsky} objects with their proper names, if any. It can only be selected if the software is configured to display deep sky objects. @endnode @node display_bayer "Bayer designation" If this @{"gadget" link define.guide/gadget} is selected, stars will be labelled with their @{"Bayer designation" link define.guide/bayer}, if they have one. It can only be selected if the software is configured to display stars. @endnode @node display_flamsteed "Flamsteed number" If this option is selected, stars will be labelled with their @{"Flamsteed number" link define.guide/flamsteed}, if they have one. It may only be selected if the software is configured to display stars. @endnode @node display_starnames "Star Names" If this @{"gadget" link define.guide/gadget} is selected, stars will be labelled with their proper names, if they have any. It can only be selected if the software is configured to display stars. @endnode @node display_phase "Show Phase" The @{"Moon" link duobjects.guide/object04401000} is famous for going through its cycle of phases. However, all planets in our solar system also exhibit phases when viewed through a telescope. @{"Mercury" link duobjects.guide/object04200000} and @{"Venus" link duobjects.guide/object04300000}, lying closer to the Sun that the Earth, can be seen to go through a complete cycle of phases, just like the Moon. The other planets, lying further than the Earth, do not appear to go through the complete cycle, but the percentage of their illuminated surface visible from the Earth does change over time. If this @{"gadget" link define.guide/gadget} is selected, "The Digital Universe" will display solar system objects with their proper phase, if the user has zoomed in sufficiently to be able to see details on the surface of the object. However, since drawing an object with the proper phase requires more time than drawing a simple disk, the software allows the user to shut off these phase calculations if desired. The option can only be selected if the software is configured to display solar system objects. @endnode @node display_features "Features & Flattening" This @{"gadget" link define.guide/gadget} enables or disables two related options of a solar system object's appearance. As with most options, enabling the gadget creates a more realistic view of the object, at the expense of taking longer to generate. The option can only be selected if the software is configured to display solar system objects. Features -------- "The Digital Universe" contains maps of the surfaces of @{"Venus" link duobjects.guide/object04300000}, @{"the Moon" link duobjects.guide/object04401000}, @{"Mars" link duobjects.guide/object04500000}, @{"Jupiter" link duobjects.guide/object04600000}, and @{"Saturn" link duobjects.guide/object04700000}. If the gadget is selected and the user is zoomed in sufficiently close to one of these bodies, the software will use these maps to generate the current appearance of the celestial body. Only the maps of the Moon and Mars are of any real practical use. Venus' surface is permanently covered in clouds, hiding its details from astronomers. The map used by "The Digital Universe" is based on radar data from the @{"Magellan" link spacecraft.guide/magellan} space probe, and shows how Venus would appear if it were stripped of its cloud cover. Jupiter and Saturn are @{"gas giant" link define.guide/gasgiantplanet} planets, with no solid surface. Different parts of the planet @{"rotate" link define.guide/rotation} at different rates (known as @{"differential rotation" link define.guide/differentialrotation}). As a result, predicting the current appearance of either of these objects is akin to predicting the weather on Earth over a long period of time. The maps used by the software for these objects simply indicate how the planets would appear if they had not changed in appearance since the @{"Voyager 2" link spacecraft.guide/voyager2} encounter. Flattening ---------- Most planets and moons in the solar system are wider at the equator than at the poles, due to their @{"rotation" link define.guide/rotation} about their axis. This effect, known as polar flattening, is especially evident with the "gas giant" planets (particularly Saturn). If the option is enabled, "The Digital Universe" will also take polar flattening into account in generating the appearance of an object. @endnode @node display_planetgrid "Show Grid" If this option is selected, "The Digital Universe" will draw the longitude/latitude grid on a solar system object. The software uses sophisticated algorithms and formulae to determine the orientation of the object, so the grid can be used to accurately determine the location of the poles and equator. The option can only be selected if the software is configured to display planets and their moons. @endnode @node display_planetnames "Sun/Planet/Moon Names" If this option is selected, the software will display names next to planets and their moons. It can only be selected if the software is configured to determine and display the position of these objects. @endnode @node display_miscobjectnames "Misc. Object Names" If this @{"gadget" link define.guide/gadget} is selected, the software will display names next to any miscellaneous objects (comets, asteroids, or Earth-orbiting satellites) that it is plotting on the screen. It can only be selected if the software is configured to determine and display the positions of these objects. @endnode @node display_limmag "Limiting Magnitude of Stars/Planets @ 20 degree field" Since "The Digital Universe" contains information on approximately 300,000 objects, it would be both time consuming and confusing if it placed all of the objects on the screen at once. To solve this problem, it uses the concept of @{"limiting magnitude" link define.guide/limitingmagnitude}. If the field of view is 20 degrees and you drag this slider @{"gadget" link define.guide/gadget} to a particular number, the software will only display objects brighter than that @{"magnitude" link define.guide/magnitude}. If you zoom in to a smaller region of sky, the software automatically compensates to show fainter objects. Likewise, if you view a larger region of sky, only brighter objects will be shown. By adjusting this bar, you can experiment with different apparent densities of stars on the screen. This bar only adjusts the limiting magnitude for stars, planets, and their moons. @endnode @node display_ngclimmag "Limiting Magnitude of Deep Sky Objects @ 20 degree field" Since "The Digital Universe" contains information on approximately 300,000 objects, it would be both time consuming and confusing if it placed all of the objects on the screen at once. To solve the problem, it uses the concept of @{"limiting magnitude" link define.guide/limitingmagnitude}. If the field of view is 20 degrees and you drag this slider @{"gadget" link define.guide/gadget} to a particular number, the software will only display @{"deep sky" link define.guide/deepsky} objects brighter than that @{"magnitude" link define.guide/magnitude}. If you zoom in to a smaller region of sky, the software automatically compensates to show fainter objects. Likewise, if you view a larger region of sky, only brighter objects will be shown. By adjusting this bar, you can experiment with different apparent densities of deep sky objects on the screen. The ability to adjust the limiting magnitude for stars and deep sky objects separately is necessary, since most deep sky objects are quite faint. However, since they are often more interesting than individual stars, the user may want to make them more prominent on the screen by making them appear brighter with this slider. @endnode @node display_misclimmag "Limiting Magnitude of Miscellaneous Objects @ 20 degree field" Since "The Digital Universe" contains information on approximately 300,000 objects, it would be both time consuming and confusing if it placed all of the objects on the screen at once. To solve the problem, it uses the concept of @{"limiting magnitude" link define.guide/limitingmagnitude}. If the field of view is 20 degrees and you drag this slider @{"gadget" link define.guide/gadget} to a particular number, the software will only display miscellaneous objects (comets, asteroids, and Earth-orbiting satellites) brighter than that @{"magnitude" link define.guide/magnitude}. If you zoom in to a smaller region of sky, the software automatically compensates to show fainter objects. Likewise, if you view a larger region of sky, only brighter objects will be shown. The ability to adjust the limiting magnitude for stars and miscellaneous objects separately is necessary, since most comets and asteroids are quite faint. However, since they are often more interesting than individual stars, the user may want to make them more prominent on the screen by making them appear brighter with this slider. @endnode @node display_save "Save Display Preferences" If this button is pressed, the options set in the @{"Display/Object Preferences" link window_display} window are used, and saved to disk. The next time you start a session with "The Digital Universe", your preferences will be loaded. If you merely wish to use your settings for the current session, click on the @{"Use" link display_use} button instead. @endnode @node display_use "Use Display Preferences" If this button is pressed, the options set in the @{"Display/Object Preferences" link window_display} window are used. However, if you quit the program and start it up again, it will use the settings last saved to disk (and not necessarily the settings you chose the last time you used the software). If you wish to make your settings permanent, you should save them to disk by clicking on the @{"Save" link display_save} button instead. @endnode @node window_fields "Field of View Preferences Window" This window allows you to preset up to 20 different fields of view. The software can then be made to instantly adjust its display to a given field of view (and orientation) with a single keypress. Simply type the desired field of view in the appropriate box. This is the angular distance (in degrees) across the field. You can also specify if the field should be flipped in the horizontal or vertical dimensions. In this way, you can customize the field of view presets to allow you to see how a particular region of the sky would appear through binoculars or your telescope with different eyepieces. Note that to make changes in this window take effect, you must press the @{"Save" link field_save} or @{"Use" link field_use} button at the bottom of the window. If you simply close the window, the software will use your old display configuration. When your fields of view are set up, you can tell the software to instantly adjust the magnification to any of the twenty fields. Simply ensure that the background window (the window upon which the simulation of the night sky is generated) is selected. Then, for a field between 0 and 9, press the number key corresponding to the desired field, using the keys on the main portion of the keyboard (NOT the numeric keypad). For a field between 10 and 19, hold down the SHIFT key while pressing a number from 0 to 9. If you wish to see the field of view circle drawn in the display, select the option labelled "Show FOV" in the @{"Display/Object Preferences" link window_display} window. Determining the Field of View in Telescopes or Binoculars ========================================================= There are two methods of determining the field of view of an optical system - either by the manufacturer's specifications, or by experiment. Specifications -------------- Sometimes binocular manufacturers specify their equipment's field of view directly, measured in degrees. If this is the case, you merely need to enter this value into the software. Other manufacturers specify the field of view in terms of `x' feet (or yards, metres, etc.) at a certain distance `y'. To determine the field of view in degrees, make sure that `x' and `y' are specified in the same units (if not, convert so that they are). If you then divide `x' by `y' and take the arctangent of the result (using a scientific calculator), you will be left with the field of view in degrees. Telescope manufacturers are unable to provide field of view specifications with their equipment, since it depends on the particular eyepiece being used. If the field of view for an eyepiece is available, it can be used in determining the effective field of view for the telescope. First, the magnification needs to be calculated. For this, you need the focal length `a' of the objective lens or mirror (the larger lens or mirror in your telescope) as well as the focal length `b' of your eyepiece. These parameters are usually readily available. The magnification of the system is then given by a/b, provided that `a' and `b' are both specified in the same units. Call this result `c'. Now, divide the field of view of the eyepiece by `c'. The result is the effective field of view of the telescope, with that particular eyepiece. The number can be entered directly into the boxes in this window. If your telescope inverts its image in either the horizontal or vertical dimensions, consider setting the appropriate "Flip Horiz." or "Flip Vert." boxes to the right. You should repeat the calculation for each eyepiece you use with your telescope. Then, the software will be able to generate the true appearance of the sky through each of your eyepieces. Experiment ---------- If you are unable to obtain one or more of the parameters necessary to calculate the field of view directly, it can be determined by experiment. Use "The Digital Universe" to find a bright star near the @{"celestial equator" link define.guide/celestialequator}. The stars in Orion's belt work good for this, if they are visible. Then, take your equipment outside, find the star, and center it in your view. If your telescope has a motor allowing it to track the stars across the sky, turn the motor off. Time how long it takes for the star to drift out of the field, expressed in seconds. Divide this number by 120, and you are left with the diameter of the field of view in degrees, which may be directly entered into the software. As before, if your telescope inverts its image in either the horizontal or vertical dimensions, consider setting the appropriate "Flip Horiz." or "Flip Vert." boxes to the right. @endnode @node field_save "Save" If you press this button, your field of view preferences will become active, and will be saved to disk. The next time you start the software, they will automatically be loaded for you. If you merely wish to use the settings for the current session, click on the @{"Use" link field_use} button instead. @endnode @node field_use "Use" The "Use" button allows you to use the field of view preferences for the current session only. If you quit the program and then restart it, the settings will be lost. If you wish to keep your settings for future sessions, click on the @{"Save" link field_save} button instead. @endnode @node window_control "Control Panel Window" This window provides buttons and @{"gadgets" link define.guide/gadget} to quickly perform common functions. The buttons on the left control the orientation and field of view of the display, while the ones on the right provide shortcuts to settings in the @{"Display/Object Preferences" link window_display} window. Unlike other windows, there is no "Use" button to make your changes take effect - instead, they are acted upon immediately. If you are interested in changing only one parameter, this is faster. However, if you have several parameters to change it may be quicker to use the Display/Object Preferences window to adjust them all at once before getting the computer to recalculate the display. In addition, you must use the Display/Object Preferences window if you would like your changes saved to disk. Additional help is available for the following gadgets and buttons: @{"Arrows " link control_arrows} @{"Zoom in " link control_zoomin} @{"Zoom out " link control_zoomout} @{"Field " link control_field} @{"Right Ascension " link control_ra} @{"Declination " link control_dec} ------------------------ @{"Display Stars " link control_star} @{"Bayer Designation " link control_bayer} @{"Flamsteed Designation " link control_flamsteed} @{"Star Names " link control_starname} @{"Constellation Figures " link control_constfigure} @{"Constellation Boundaries" link control_constboundaries} @{"Constellation Names " link control_constnames} @{"RA/Dec Grid " link control_grid} @{"Horizon " link control_horizon} @{"Deep Sky Objects " link control_deepsky} @{"NGC Number " link control_ngc} @{"Messier Number " link control_messier} @{"Deep Sky Name " link control_deepskyname} @{"Miscellaneous Objects " link control_miscobject} @{"Misc. Object Name " link control_miscobjname} @{"Earth's Shadow " link control_shadow} @{"Flip Horizontal " link control_flipx} @{"Flip Vertical " link control_flipy} @{"Sun/Planet/Moon " link control_ssystem} @{"Phase " link control_phase} @{"Features " link control_features} @{"Planetary Grid " link control_planetgrid} @{"Sun/Planet/Moon Names " link control_ssystemname} @{"Star Trails " link control_startrail} @{"Field of View " link control_fov} @{"Display Time " link control_time} @endnode @node control_arrows "Arrows" The arrow buttons in the Control Panel allow the user to pan the display around the sky. In general, clicking on one of these buttons moves the center of your field of view in the direction of the arrow. Specifically, the function of these arrows depends on whether you are in @{"Planetarium" link menu_planetarium} or @{"Local Sky" link menu_localsky} mode. If you are in Planetarium mode, the arrows move your view in the directions of the compass (north, south, east, west, etc.). In Local Sky Mode, they move your field of view left, right, up or down. @endnode @node control_zoomout "Zoom Out" Selecting this button enlarges the field of view by a factor of 1.5. @endnode @node control_zoomin "Zoom In" This button reduces the field of view by a factor of 1.5. @endnode @node control_field "Field" This @{"requester" link define.guide/gadget} allows you to enter the diameter of the field of view directly. It may be specified in one of two ways - by decimal degrees (such as 42.5) or in degrees, minutes, and seconds separated by colons (such as 45:32:25). After typing the desired field of view, press the ENTER key. The display will be adjusted to the exact field that you specified. @endnode @node control_ra "Right Ascension" The @{"Right Ascension" link define.guide/rightascension} of the center of your field of view may be entered into this @{"requester" link define.guide/gadget}. It may be specified in one of two ways - by decimal hours (such as 12.4) or in hours, minutes, and seconds separated by colons (such as 10:24:35). After typing the new right ascension, press the ENTER key. The display will immediately be adjusted so that the center of the field is defined by the contents of the right ascension and @{"declination" link control_dec} requesters in the Control Panel window. @endnode @node control_dec "Declination" The @{"Declination" link define.guide/declination} of the center of your field of view may be entered into this @{"requester" link define.guide/gadget}. It may be specified in one of two ways - by decimal degrees (such as -45.3) or in degrees, minutes, and seconds separated by colons (such as 56:23:54). After typing the new declination, press the ENTER key. The display will be immediately adjusted so that the center of the field is defined by the contents of the @{"right ascension" link control_ra} and declination requesters in the Control Panel window. @endnode @node control_star "Stars" This button is provided as a shortcut to the @{"Stars" link display_stars} @{"gadget" link define.guide/gadget} in the @{"Display/Object Preferences" link window_display} window. @endnode @node control_bayer "Bayer designation" This button is provided as a shortcut to the @{"Bayer designation" link display_bayer} @{"gadget" link define.guide/gadget} in the @{"Display/Object Preferences" link window_display} window. @endnode @node control_flamsteed "Flamsteed designation" This button is provided as a shortcut to the @{"Flamsteed designation" link display_flamsteed} @{"gadget" link define.guide/gadget} in the @{"Display/Object Preferences" link window_display} window. @endnode @node control_starname "Star Names" This button is provided as a shortcut to the @{"Star Names" link display_starnames} @{"gadget" link define.guide/gadget} in the @{"Display/Object Preferences" link window_display} window. @endnode @node control_constfigure "Constellation Figures" This button is provided as a shortcut to the @{"Constellation Figures" link display_figures} @{"gadget" link define.guide/gadget} in the @{"Display/Object Preferences" link window_display} window. @endnode @node control_constboundaries "Constellation Boundaries" This button is provided as a shortcut to the @{"Constellation Boundaries" link display_boundaries} @{"gadget" link define.guide/gadget} in the @{"Display/Object Preferences" link window_display} window. @endnode @node control_constnames "Constellation Names" This button is provided as a shortcut to the @{"Constellation Names" link display_names} @{"gadget" link define.guide/gadget} in the @{"Display/Object Preferences" link window_display} window. @endnode @node control_grid "RA/Dec Grid" This button is provided as a shortcut to the @{"RA/Dec Grid" link display_radec} @{"gadget" link define.guide/gadget} in the @{"Display/Object Preferences" link window_display} window. @endnode @node control_horizon "Horizon" This button is provided as a shortcut to the @{"Horizon" link display_horizon} @{"gadget" link define.guide/gadget} in the @{"Display/Object Preferences" link window_display} window. @endnode @node control_deepsky "Deep Sky Objects" This button is provided as a shortcut to the @{"Deep Sky Objects" link display_galaxy} @{"gadget" link define.guide/gadget} in the @{"Display/Object Preferences" link window_display} window. @endnode @node control_ngc "NGC/IC #" This button is provided as a shortcut to the @{"NGC/IC #" link display_ngc} @{"gadget" link define.guide/gadget} in the @{"Display/Object Preferences" link window_display} window. @endnode @node control_messier "Messier #" This button is provided as a shortcut to the @{"Messier #" link display_messier} @{"gadget" link define.guide/gadget} in the @{"Display/Object Preferences" link window_display} window. @endnode @node control_deepskyname "Deep Sky Names" This button is provided as a shortcut to the @{"Deep Sky Names" link display_deepskynames} @{"gadget" link define.guide/gadget} in the @{"Display/Object Preferences" link window_display} window. @endnode @node control_miscobject "Miscellaneous Objects" This button is provided as a shortcut to the @{"Miscellaneous Objects" link display_miscobject} @{"gadget" link define.guide/gadget} in the @{"Display/Object Preferences" link window_display} window. @endnode @node control_miscobjname "Misc. Object Names" This button is provided as a shortcut to the @{"Misc. Object Names" link display_miscobjectnames} @{"gadget" link define.guide/gadget} in the @{"Display/Object Preferences" link window_display} window. @endnode @node control_shadow "Earth's Shadow" This button is provided as a shortcut to the @{"Earth's Shadow" link display_shadow} @{"gadget" link define.guide/gadget} in the @{"Display/Object Preferences" link window_display} window. @endnode @node control_flipx "Flip Horizontal" This button is provided as a shortcut to the @{"Flip Horizontal" link display_flip} @{"gadget" link define.guide/gadget} in the @{"Display/Object Preferences" link window_display} window. @endnode @node control_flipy "Flip Vertical" This button is provided as a shortcut to the @{"Flip Vertical" link display_flip} @{"gadget" link define.guide/gadget} in the @{"Display/Object Preferences" link window_display} window. @endnode @node control_ssystem "Sun/Planet/Moon" This button is provided as a shortcut to the @{"Sun/Planet/Moon" link display_ssystem} @{"gadget" link define.guide/gadget} in the @{"Display/Object Preferences" link window_display} window. @endnode @node control_phase "Show Phase" This button is provided as a shortcut to the @{"Show Phase" link display_phase} @{"gadget" link define.guide/gadget} in the @{"Display/Object Preferences" link window_display} window. @endnode @node control_features "Features & Flattening" This button is provided as a shortcut to the @{"Features & Flattening" link display_features} @{"gadget" link define.guide/gadget} in the @{"Display/Object Preferences" link window_display} window. @endnode @node control_planetgrid "Show Grid" This button is provided as a shortcut to the @{"Show Grid" link display_planetgrid} @{"gadget" link define.guide/gadget} in the @{"Display/Object Preferences" link window_display} window. @endnode @node control_ssystemname "Sun/Planet/Moon Names" This button is provided as a shortcut to the @{"Sun/Planet/Moon Names" link display_planetnames} @{"gadget" link define.guide/gadget} in the @{"Display/Object Preferences" link window_display} window. @endnode @node control_startrail "Star Trails" This button is provided as a shortcut to the @{"Star Trails" link display_startrails} @{"gadget" link define.guide/gadget} in the @{"Display/Object Preferences" link window_display} window. @endnode @node control_fov "Show FOV" This button is provided as a shortcut to the @{"Show FOV" link display_fov} @{"gadget" link define.guide/gadget} in the @{"Display/Object Preferences" link window_display} window. @endnode @node control_time "Show Time" This button is provided as a shortcut to the @{"Show Time" link display_time} @{"gadget" link define.guide/gadget} in the @{"Display/Object Preferences" link window_display} window. @endnode @node window_time "Time Control Window" This window contains the controls necessary to set the current time and time advancement criteria used by the software. Help is available for the following @{"gadgets" link define.guide/gadget}: Set Time ======== @{"Local Mean Time " link time_local} @{"Universal Mean Time " link time_universal} @{"Dynamical Time " link time_dynamical} @{"Local Sidereal Time " link time_localsidereal} @{"Universal Sidereal Time " link time_universalsidereal} @{"Delta T " link time_deltat} @{"Estimate " link time_estimatedeltat} @{"Current/Other Time " link time_currenttime} @{"Epoch " link time_epoch} Time Advancement ================ @{"Advance " link time_advance} @{"Advance Units " link time_advanceunit} @{"Every " link time_every} @{"Every Units " link time_everyunit} @{"Automatic/Manual Advance" link time_autoadvance} @{"Lock onto " link time_lockonto} @{"Object list " link time_lockobjects} @{"Use " link time_use} @endnode @node time_local "Local Mean Time" In these two boxes you can enter your local time - the civil time kept by clocks in your time zone. You can enter the time in "conventional" format (yyyy/mm/dd hh:mm:ss.s) in the left hand box or as a @{"Julian Date" link define.guide/juliandate} in the right hand box. After entering the time, press ENTER. The time you entered will then be converted to all of the other standards displayed in the window and they will be updated. You must press the @{"Use" link time_use} button at the bottom of the window for your changes to take effect. See also: @{"Description of Local and Universal Time" link astro.guide/universaltime} @{"Entering Dates B.C." link time_bc}, @{"Leap Years" link define.guide/leapyear} @endnode @node time_universal "Universal Mean Time" In these two boxes you can enter the Universal Mean Time - the civil time kept by clocks in Greenwich, England. You can enter the time in "conventional" format (yyyy/mm/dd hh:mm:ss.s) in the left hand box or as a @{"Julian Date" link define.guide/juliandate} in the right hand box. After entering the time, press ENTER. The time you entered will then be converted to all of the other standards displayed in the window and they will be updated. You must press the @{"Use" link time_use} button at the bottom of the window for your changes to take effect. See also: @{"Description of Local and Universal Time" link astro.guide/universaltime} @{"Entering Dates B.C." link time_bc}, @{"Leap Years" link define.guide/leapyear} @endnode @node time_dynamical "Dynamical Time" In these two boxes you can enter the current Dynamical Time. Dynamical Time is that used by professional astronomers, closely related to time as kept by atomic clocks. Due to irregularities in the Earth's rotation, the difference between Dynamical Time and Greenwich Mean Time varies irregularly. The difference (in seconds) is specified in the @{"Delta T" link time_deltat} @{"requester" link define.guide/gadget}. You can enter the time in "conventional" format (yyyy/mm/dd hh:mm:ss.s) in the left hand box, or as a @{"Julian Date" link define.guide/juliandate} in the right hand box. After entering the time, press ENTER. The time you entered will then be converted to all of the other standards displayed in the window and they will be updated. You must press the @{"Use" link time_use} button at the bottom of the window for your changes to take effect. See also: @{"Description of Dynamical Time" link astro.guide/dynamicaltime} @{"Entering Dates B.C." link time_bc}, @{"Leap Years" link define.guide/leapyear} @endnode @node time_localsidereal "Local Sidereal Time" Your Local Sidereal Time can be entered in these two boxes. It can be input in "conventional" format (yyyy/mm/dd hh:mm:ss.s) in the left hand box, or as a @{"Julian Date" link define.guide/juliandate} in the right hand box. After entering the time, press ENTER. The time you entered will then be converted to all of the other standards displayed in the window and they will be updated. You must press the @{"Use" link time_use} button at the bottom of the window for your changes to take effect. See also: @{"Description of Sidereal Time" link astro.guide/siderealtime} @{"Entering Dates B.C." link time_bc} @endnode @node time_universalsidereal "Universal Sidereal Time" The current Universal Sidereal Time can be entered in these two boxes. It can be input in "conventional" format (yyyy/mm/dd hh:mm:ss.s) in the left hand box, or as a @{"Julian Date" link define.guide/juliandate} in the right hand box. After entering the time, press ENTER. The time you entered will then be converted to all of the other standards displayed in the window and they will be updated. You must press the @{"Use" link time_use} button at the bottom of the window for your changes to take effect. See also: @{"Description of Sidereal Time" link astro.guide/siderealtime} @{"Entering Dates B.C." link time_bc} @endnode @node time_bc "Entering Dates B.C." Since the definition of our current calendar was introduced in stages, there are several inconsistencies. For example, in 1582 it was found that the calendar in use was no longer synchronized with the seasons, so ten days were dropped in an effort to restore things to normal (see the definition of a @{"leap year" link define.guide/leapyear} for more information). Another inconsistency arises from the fact that there was no year 0. 1 B.C. was immediately followed by 1 A.D. In order to account for this fact, "The Digital Universe" specifies years (and expects you to specify them) in the following manner: Year Specification ---- ------------- 2 A.D. 2 1 A.D. 1 1 B.C. 0 2 B.C. -1 3 B.C. -2 etc. Thus, a moment like 2:00 pm on August 2, 5 B.C. would be specified like: -4/8/2 14:00:00 @endnode @node time_deltat "Delta T" Since the Earth is gradually (and erratically) slowing down in its rotation, Universal Time (based on the rotation of the Earth) and Dynamical Time (related to atomic time, and representing a uniform timescale) differ in an unpredictable manner. You can specify a value (in seconds) for the difference between dynamical and universal time in this box. Since all calculations are done using dynamical time, and civil timekeeping is based on universal time, results are only as accurate as the specification for Delta T. See also: @{"Estimate Delta T" link time_estimatedeltat} @endnode @node time_estimatedeltat "Estimate Delta T" "The Digital Universe" contains a historical record of the value of @{"Delta T" link time_deltat} from 1620 to the present. If you are simulating the appearance of the night sky during this period and press the "Estimate" button, an appropriate value for Delta T will be inserted into the box to the left. @endnode @node time_currenttime "Current/Other Time" This @{"radio button" link define.guide/radiobutton} specifies whether the software is using the current time (as kept by the Amiga's internal clock) or some other time. If "Current Time" is selected, the time @{"requesters" link define.guide/gadget} above will represent the time that the @{"Time Control Window" link window_time} was opened, or the time that "Current Time" was selected. In addition, the time will be reset at the instant that @{"Use" link time_use} is depressed. In this way, it is easy to synchronize "The Digital Universe" to keep pace with the current time. On the other hand, if "Other Time" is selected, "The Digital Universe" will not read the internal clock to determine the time. "Other Time" will automatically be selected if the time is changed in one of the boxes above. @endnode @node time_epoch "Epoch" You are able to specify the @{"epoch" link define.guide/epoch} used for calculations in this box. Four different entry formats are possible: Jnnnn.n (J2000.0) - specifies the instant at the start of a @{"Julian Year" link define.guide/julianyear} Bnnnn.n (B1950.0) - specifies the instant at the start of a @{"Besselian Year" link define.guide/besselianyear} JDnnnnnnn.nn - specifies the epoch as a particular @{"Julian Date" link define.guide/juliandate} DATE - specifies the epoch of date. The epoch used is that represented by the date and time in the boxes above. @endnode @node time_advance "Advance" You are able to enter a number in this box which (in combination with the @{"Advance Units" link time_advanceunit} @{"gadget" link define.guide/gadget} directly to the right) specifies how much time the software is to advance by, either manually or automatically. @endnode @node time_advanceunit "Advance Units" Use this box to select which unit of time (used in conjunction with the @{"Advance" link time_advance} @{"gadget" link define.guide/gadget} directly to the left) should be used in manual and automatic time advancement. You can choose from: seconds minutes hours days @{"Gregorian Years " link define.guide/gregorianyear} @{"Julian Years " link define.guide/julianyear} @{"Tropical Years " link define.guide/besselianyear} @{"Sidereal Years " link define.guide/siderealyear} @{"Anomalistic Years" link define.guide/anomalisticyear} @{"Eclipse Years " link define.guide/eclipseyear} @{"Gaussian Years " link define.guide/gaussianyear} @endnode @node time_every "Every" If automatic advancement is selected with the @{"Automatic/Manual Advance" link time_autoadvance} @{"radio button" link define.guide/radiobutton}, the software needs to know how frequently to update the screen. You can use this @{"requester" link define.guide/gadget} in conjunction with the @{"Every Units" link time_everyunit} @{"gadget" link define.guide/gadget} to the right in order to specify this interval. @endnode @node time_everyunit "Every Units" If automatic advancement is selected with the @{"Automatic/Manual Advance" link time_autoadvance} @{"radio button" link define.guide/radiobutton}, the software needs to know how frequently to update the screen. You can use this @{"gadget" link define.guide/gadget} in conjunction with the @{"Every" link time_everyunit} @{"requester" link define.guide/gadget} to the left in order to specify this interval. You can choose from: seconds minutes hours days @{"Gregorian Years " link define.guide/gregorianyear} @{"Julian Years " link define.guide/julianyear} @{"Tropical Years " link define.guide/besselianyear} @{"Sidereal Years " link define.guide/siderealyear} @{"Anomalistic Years" link define.guide/anomalisticyear} @{"Eclipse Years " link define.guide/eclipseyear} @{"Gaussian Years " link define.guide/gaussianyear} @endnode @node time_autoadvance "Automatic/Manual Advance" These @{"radio buttons" link define.guide/radiobutton} allow you to specify whether time should be advanced automatically or manually. It is advanced by the amount specified by the @{"Advance" link time_advance} and @{"Advance Unit" link time_advanceunit} @{"gadgets" link define.guide/gadget}. If manual advancement is selected, the user can step forward or backward through time with the right and left arrow keys respectively. If automatic advancement is selected, time progresses forward at an interval specified by the @{"Every" link time_every} and @{"Every Unit" link time_everyunit} gadgets. If the computer is in automatic advancement mode, it stops immediately after manual advancement is depressed - you don't have to press @{"Use" link time_use} first. @endnode @node time_lockonto "Lock Onto" As time progresses, either manually or automatically, "The Digital Universe" needs to know what it should be "locked onto". This information is specified with this @{"radio button" link define.guide/radiobutton} and possibly the @{"Object list" link time_lockobjects} to the right. If "RA/Dec" is selected, the computer will keep the center of its field of view locked onto the same @{"right ascension" link define.guide/rightascension} and @{"declination" link define.guide/declination} as time progresses. This is useful if you wish to keep looking at the same stars. If "Alt/Az" is selected, the computer will keep the center of its field of view locked onto the same @{"altitude" link define.guide/altitude} and @{"azimuth" link define.guide/azimuth} as time progresses. As a result, the horizon stays fixed in place and you can see the motion of the stars across the sky. If "Object" is selected, you will be able to select an object to lock onto in the list to the right. In this way, you can follow a planet, moon, asteroid, comet, or Earth-orbiting satellite as it travels across the sky. @endnode @node time_lockobjects "Object List" If "Object" is selected in the @{"Lock Onto" link time_lockonto} @{"radio button" link define.guide/radiobutton} to the left, you are able to select an object from this list to lock onto as time advances. In this way, you can follow a planet, moon, asteroid, comet, or Earth-orbiting satellite as it travels across the sky. @endnode @node time_use "Use" Once you have made changes to the @{"Time Control" link window_time} window, you need to press this button for the changes to take effect. @endnode @node window_miscobjs "Miscellaneous Objects" This window provides an interface whereby you can specify which miscellaneous objects (comets, asteroids, or Earth-orbiting satellites) that "The Digital Universe" should consider in generating a view of the sky. Help is available for the following @{"gadgets" link define.guide/gadget}: @{"Orbit File " link misc_orbitfile} @{"Objects in the File" link misc_filelist} @{"Selected Objects " link misc_selected} @{"Sort By " link misc_sortby} @{"Edit " link misc_edit} @{"Add " link misc_add} @{"Remove " link misc_remove} @{"Save " link misc_save} @endnode @node misc_orbitfile "Orbit File" You can use this @{"requester" link define.guide/gadget} to specify the file that you wish to obtain miscellaneous object orbits from. By convention, these orbit files should be placed in the DU:data/orbits directory. You may enter the filename (complete with path) into the box provided. If preferred, you can click on the image to the right of the input box to bring up a file requester to choose the file. "The Digital Universe" uses files in the "Universal Orbit Format", developed specifically for use with this package. This format allows for @{"orbital elements" link define.guide/orbitalelements} of asteroids, comets, or Earth-orbiting satellites to be stored and retrieved. Several utility programs exist to convert orbital element files in a variety of formats into the "Universal Orbit Format" - see @{"Utility Programs" link utilities} for more information. The current version of this software is restricted to there being no more than 1000 objects in an individual file. As a result, the databases for comets, asteroids, and Earth-orbiting satellites are split up into several different files: asteroids_numbered_1.uof - Numbered asteroids from 1 to 1000 asteroids_numbered_2.uof - Numbered asteroids from 1001 to 2000 asteroids_numbered_3.uof - Numbered asteroids from 2001 to 3000 asteroids_numbered_4.uof - Numbered asteroids from 3001 to 4000 asteroids_numbered_5.uof - Numbered asteroids from 4001 to 5000 asteroids_numbered_6.uof - Numbered asteroids from 5001 to 6000 asteroids_numbered_7.uof - Numbered asteroids from 6001 to 7000 asteroids_precise_1.uof - Designated asteroids from 29TD1 to 81WS1 asteroids_precise_2.uof - Designated asteroids from 81WE9 to 89SR asteroids_precise_3.uof - Designated asteroids from 89SA3 to 92CU asteroids_precise_4.uof - Designated asteroids from 92DA to 94RZ asteroids_precise_5.uof - Designated asteroids from 94RCB to 95DW comets_1.uof - Comets with perihelion dates prior to Sep, 1973 comets_2.uof - Comets with perihelion dates from Oct, 1973 to Sep, 2042 comets_3.uof - Comets with perihelion dates after Oct, 2042 misc.uof - File to which the user can add orbit information for newly discovered objects satellite_molczan.uof - Earth-orbiting satellites from Ted Molczan satellite_tle.uof - Earth-orbiting satellites from T. S. Kelso When the program is first started, it defaults to loading comets_2.uof. NOTE: Since this is a demonstration version of "The Digital Universe", only the files "satellite_molczan.uof" and "comets_2.uof" are included. There are a few points which should be remembered about the files. The brightest asteroids are those in the asteroids_numbered files. See @{"The Brightest Asteroids" link brightasteroids} for a list of the hundred brightest asteroids, most of which can be found in asteroids_numbered_1.uof. Since periodic comets are typically in highly @{"eccentric" link define.guide/eccentricity} orbits and are strongly @{"perturbed" link define.guide/perturbation} by the larger planets, their orbits are often substantially different from one appearance to the next. As a result, a separate orbit is provided for each appearance of these comets. When predicting the path of a comet, it is best to use the orbit with the @{"perihelion" link define.guide/perihelion} date closest to the time of interest. As comets and asteroids are continually being discovered, "The Digital Universe" allows the user to enter orbital elements manually. All additions should be made to the misc.uof file. Updates to the asteroids and comets databases are available from Jost Jahn. If you require more up-to-date information than that supplied with the software, you can obtain the new data sets directly from him. His address is: Jost Jahn Neustädter Straße 11 29389 Bodenteich Germany Tel.: 05824-3197 FAX: 0581-14824 Internet: j.jahn@abbs.heide.de At the time this documentation was written, he was charging DM 30 (30 Deutschmarks) for a new data set. You will need some of the @{"utility programs" link utilities} supplied with the software to convert between his file formats and the "Universal Orbit Format" used by "The Digital Universe". Earth-orbiting satellites are strongly affected by atmospheric drag and other phenomenae. While "The Digital Universe" uses NORAD's highly accurate SGP4 model to consider these effects, the most accurate results are always obtained with recent satellite data sets. This software package contains the program @{"tle2uof" link tle2uof} to convert between NORAD's standard three-line element format and the "Universal Orbit Format". Two good sources of updated satellite orbit information are available to users with a modem: Dr. T. S. Kelso's (email: tkelso@afit.af.mil) orbital elements: - Celestial BBS at (334) 409-9280 - Internet anonymous FTP at archive.afit.af.mil (file: /pub/space/tle.new) Ted J. Molczan's orbital elements: - Canadian Space Society BBS at (905) 458-5907 - Internet anonymous FTP at kilroy.jpl.nasa.gov (file: /pub/space/elements/molczan/new_molc.Z) In addition, satellite orbit files pre-converted to the "Universal Orbit Format" will periodically be available at our own Internet World Wide Web (WWW) site at the following URL: http://www.syz.com @endnode @node misc_filelist "Objects in the File" This list shows the objects contained in the file selected with the @{"Orbit File" link misc_orbitfile} @{"requester" link define.guide/gadget} above. To add an object to your @{"Selected Objects" link misc_selected} list (necessary for the computer to calculate the position of that object), double click the mouse pointer on the object. If you wish to examine or change the orbital element data for any object, click once on the object and then select the @{"Edit" link misc_edit} button at the bottom of the window. Ensure that you only change information in the "misc.uof" file! @endnode @node misc_selected "Selected Objects" This list shows the miscellaneous objects which "The Digital Universe" will consider when displaying the appearance of the sky. Items are added to this list by double clicking the mouse pointer on objects presented in the @{"Objects in the File" link misc_filelist} list, and are removed by clicking once on the object to remove, then selecting the @{"Remove" link misc_remove} button at the bottom of the window. There is a limit of 100 miscellaneous objects which can be selected at any one time. If you close the window, the display will be recalculated to consider any new miscellaneous objects that you might have added. If you would like to save your current list of miscellaneous objects so that it is loaded the next time "The Digital Universe" is started, you must click on the @{"Save" link misc_save} button at the bottom of the window. @endnode @node misc_sortby "Sort By.." This @{"gadget" link define.guide/gadget} enables you to specify how you want the objects in the @{"list" link misc_filelist} above to be sorted. If the list contains comets or asteroids, you can choose between an alphabetical sorting by name or a chronological ordering by @{"perihelion" link define.guide/perihelion} date. If the list contains Earth-orbiting satellites, you can choose between an alphabetical list by name or a chronological ordering by @{"epoch" link define.guide/epoch}. Some satellites in low Earth orbit are strongly affected by the atmosphere and other phenomenae in unpredictable manners. As a result, it is important to ensure that you obtain more recent orbital information for a satellite if its Epoch Date is getting old. See @{"Orbit File" link misc_orbitfile} for information on obtaining more recent data sets. @endnode @node misc_edit "Edit" If you select on an object in the @{"list" link misc_filelist} above and then press the "Edit" button, the @{"Miscellaneous Object Orbit Entry" link window_editobject} window will appear enabling you to edit the @{"orbital elements" link define.guide/orbitalelements} and related information for the object. Ensure that you only edit or add orbits to the misc.uof file! @endnode @node misc_add "Add" If there are less than 1000 objects in the current file, clicking on this entry brings up the @{"Miscellaneous Object Orbit Entry" link window_editobject} window allowing you to add additional objects. Ensure that you only edit or add orbits to the misc.uof file! @endnode @node misc_remove "Remove" If you click on an object in the @{"Selected Objects" link misc_selected} list and then press the "Remove" button, the object will be removed from the list. The computer will no longer consider the position of that object when generating a view of the sky. @endnode @node misc_save "Save" Pressing the "Save" button allows you to save the contents of the @{"Selected Objects" link misc_selected} list. The next time you start "The Digital Universe", these objects will automatically be loaded into your "Selected Objects" list. If you merely want to use the list of selected objects without saving your preferences to disk, just close the @{"Miscellaneous Objects" link window_miscobjs} window. @endnode @node brightasteroids "The Brightest Asteroids" The following table provides the names and mean @{"opposition" link define.guide/opposition} @{"magnitudes" link define.guide/magnitude} of the 100 brightest asteroids. Keep in mind that since asteroid orbits are fairly eccentric, an asteroid may appear substantially brighter or fainter at any particular opposition. "The Digital Universe" can simulate the position of any of these asteroids, most of which can be found in the orbit file entitled "asteroids_numbered_1.uof". Asteroid Opposition Magnitude -------- -------------------- 4 Vesta 5.7 1 Ceres 6.8 2 Pallas 7.6 7 Iris 8.1 6 Hebe 8.4 15 Eunomia 8.5 3 Juno 8.6 8 Flora 8.6 29 Amphitrite 8.8 9 Metis 8.9 18 Melpomene 8.9 20 Massalia 9.2 532 Herculina 9.3 40 Harmonia 9.3 11 Parthenope 9.3 14 Irene 9.4 27 Euterpe 9.5 39 Laetitia 9.5 10 Hygiea 9.6 89 Julia 9.6 16 Psyche 9.6 349 Dembowska 9.7 12 Victoria 9.7 44 Nysa 9.7 192 Nausikaa 9.8 13 Egeria 9.8 19 Fortuna 9.9 5 Astraea 9.9 51 Nemausa 9.9 230 Athamantis 9.9 354 Eleonora 9.9 704 Interamnia 10.0 43 Ariadne 10.0 21 Lutetia 10.1 115 Thyra 10.1 324 Bamberga 10.1 23 Thalia 10.1 30 Urania 10.1 63 Ausonia 10.2 22 Kalliope 10.2 68 Leto 10.3 42 Isis 10.3 433 Eros 10.3 4544 Xanthus 10.3 80 Sappho 10.3 52 Europa 10.4 511 Davida 10.4 471 Papagena 10.4 25 Phocaea 10.5 37 Fides 10.5 88 Thisbe 10.5 41 Daphne 10.6 28 Bellona 10.6 17 Thetis 10.6 32 Pomona 10.6 196 Philomela 10.6 346 Hermentari 10.6 129 Antigone 10.6 451 Patientia 10.6 409 Aspasia 10.7 79 Eurynome 10.7 26 Proserpina 10.7 71 Niobe 10.7 216 Kleopatra 10.8 387 Aquitania 10.8 45 Eugenia 10.8 194 Prokne 10.8 287 Nephthys 10.8 85 Io 10.8 60 Echo 10.8 92 Undina 10.8 270 Anahita 10.9 97 Klotho 10.9 31 Euphrosyne 10.9 654 Zelinda 10.9 128 Nemesis 10.9 69 Hesperia 10.9 135 Hertha 10.9 64 Angelina 10.9 67 Asia 11.0 103 Hera 11.0 48 Doris 11.0 54 Alexandra 11.0 389 Industria 11.0 185 Eunike 11.0 2063 Bacchus 11.0 1566 Icarus 11.0 4769 Castalia 11.0 173 Ino 11.1 148 Gallia 11.1 385 Ilmatar 11.1 198 Ampella 11.1 111 Ate 11.1 144 Vibilia 11.1 93 Minerva 11.1 386 Siegena 11.1 105 Artemis 11.1 345 Tercidina 11.2 344 Desiderata 11.2 674 Rachele 11.2 @endnode @node window_findssystem "The Sun, Planets, and Moons" By clicking on the Sun, a planet, or a moon, "The Digital Universe" will adjust the display so that the object of interest is centered in the field of view. If the object is too dim to show up with your current settings for @{"limiting magnitude" link define.guide/limitingmagnitude} in the @{"Display/Object Preferences" link window_display} window, the computer will zoom in until the object is visible. @endnode @node window_findconstellation "Constellation Selection" This window contains a list of all currently recognized @{"constellations" link define.guide/constellation}. If you click on an object in the list, "The Digital Universe" will adjust the display so that the constellation is centered on the screen and fills the field of view. The constellation itself will only be visible if you have selected @{"Constellation Figures" link display_figures} or @{"Boundaries" link display_boundaries} in the @{"Display/Object Preferences" link window_display} window. @endnode @node window_findstar "Star Selection" This window allows you to find a star of interest. Stars can be located based upon a number of different designations - Proper Name, @{"Bayer designation" link define.guide/bayer}, @{"Flamsteed number" link define.guide/flamsteed}, Yale Bright Star (YBS) catalogue number, Smithsonian Astrophysical Observatory (SAO) catalogue number, or the Henry Draper (HD) catalogue number. The general process in selecting a star is to first pick the type of designation that you will be searching for, and then fill in the appropriate blanks or choosing the appropriate items from lists. When you are done, your search criteria will be entered automatically into the @{"Criteria" link findstar_criteria} @{"requester" link define.guide/gadget} at the bottom of the screen. If you are satisfied with your request, press the @{"Search" link findstar_search} button and the computer will find the star of interest (if it exists) and center it on the screen. If you prefer, you can enter the search criteria directly in the blank before pressing "Search". This can be faster than getting the computer to fill in the blank for you once you know the format that the entries should take. Help is also available for the following items: @{"Star Name " link findstar_name} @{"Bayer Designation" link findstar_bayer} @{"Flamsteed Number " link findstar_flamsteed} @{"YBS Number " link findstar_ybs} @{"SAO Number " link findstar_sao} @{"HD Number " link findstar_hd} @{"Criteria " link findstar_criteria} @{"Search " link findstar_search} @endnode @node findstar_name "Star Name" If "Star Name" is selected, a list of currently recognized star names is displayed. To find a star from this list, just click on the star of interest and then press the @{"Search" link findstar_search} button below. @endnode @node findstar_bayer "Bayer Designation" If you are finding a star by @{"Bayer designation" link define.guide/bayer}, you must click on both the Greek letter and the @{"constellation" link define.guide/constellation} name to identify a unique object. Once you have entered your request, press the @{"Search" link findstar_search} button to find the object. Some combinations of Greek letters and constellations are not associated with any particular star (there is no star designated Psi Arae, for example). In these cases, you will be presented with a little window describing that the object of interest could not be found. @endnode @node findstar_flamsteed "Flamsteed Number" You can find a star by @{"Flamsteed Number" link define.guide/flamsteed} if you enter a number into the "Flamsteed #" box and press ENTER as well as pick a @{"constellation" link define.guide/constellation} from the list on the right. Once your request appears in the @{"Criteria" link findstar_criteria} box, you can press the @{"Search" link findstar_search} button to try and find the object. If it cannot be found, a window will appear to notify you. Otherwise, the star will appear in the center of the screen. @endnode @node findstar_ybs "YBS Number" To find a star by its Yale Bright Star (YBS) Catalogue number, just enter the number into the box provided and hit ENTER. If you are satisfied with the result appearing in the @{"Criteria" link findstar_criteria} box, press the @{"Search" link findstar_search} button. @endnode @node findstar_sao "SAO Number" To find a star by its Smithsonian Astrophysical Observatory (SAO) Catalogue number, just enter the number into the box provided and hit ENTER. If you are satisfied with the result appearing in the @{"Criteria" link findstar_criteria} box, press the @{"Search" link findstar_search} button. @endnode @node findstar_hd "HD Number" To find a star by its Henry Draper (HD) Catalogue number, just enter the number into the box provided and hit ENTER. If you are satisfied with the result appearing in the @{"Criteria" link findstar_criteria} box, press the @{"Search" link findstar_search} button. @endnode @node findstar_criteria "Criteria" This box performs two functions. If you enter a search request by using the @{"gadgets" link define.guide/gadget} above the box, the request will be composed and appear within. Alternately, you can enter a search criteria directly into this box if you use the proper entry format. You must press @{"Search" link findstar_search} to get the computer to find the object of interest. @endnode @node findstar_search "Search" After a search criteria has been composed and appears in the @{"Criteria" link findstar_criteria} box (either automatically or manually), you must press the "Search" button to allow the computer to try and find the object of interest. @endnode @node window_finddeepsky "Deep Sky Object Selection" This window allows you to find a @{"deep sky" link define.guide/deepsky} object of interest. You may search according to a number of different designations - Proper Name, @{"Messier number" link define.guide/messier}, @{"NGC number" link define.guide/ngc}, or @{"IC number" link define.guide/ic}. The general process in selecting a deep sky object is to first pick the type of designation that you will be searching for, and then fill in the appropriate blanks or choosing the appropriate items from lists. When you are done, your search criteria will be entered automatically into the @{"Criteria" link finddeepsky_criteria} @{"requester" link define.guide/gadget} at the bottom of the screen. If you are satisfied with your request, press the @{"Search" link finddeepsky_search} button and the computer will find the object of interest (if it exists) and center it on the screen. If you prefer, you can enter the search criteria directly in the blank before pressing "Search". This can be faster than getting the computer to fill in the blank for you once you know the format that the entries should take. Help is also available for the following items: @{"Object Name " link finddeepsky_name} @{"Messier number" link finddeepsky_messier} @{"NGC number " link finddeepsky_ngc} @{"IC number " link finddeepsky_ic} @{"Criteria " link finddeepsky_criteria} @{"Search " link finddeepsky_search} @endnode @node finddeepsky_name "Deep Sky Object Name" If "Object Name" is selected, a list of currently recognized @{"deep sky" link define.guide/deepsky} object names is displayed. To find an object from this list, just click on the name of interest and press the @{"Search" link finddeepsky_search} button below. @endnode @node finddeepsky_messier "Messier Number" If "Messier Number" is selected, you can find a @{"deep sky" link define.guide/deepsky} object by @{"Messier number" link define.guide/messier}. Just type the Messier number in the box provided and hit ENTER. A search request will be composed in the @{"Criteria" link finddeepsky_criteria} box. If it is acceptable, press the @{"Search" link finddeepsky_search} button to begin the search. @endnode @node finddeepsky_ngc "NGC Number" If "NGC Number" is selected, you can find a @{"deep sky" link define.guide/deepsky} object by @{"NGC number" link define.guide/ngc}. Just type the NGC number in the box provided and hit ENTER. A search request will be composed in the @{"Criteria" link finddeepsky_criteria} box. If it is acceptable, press the @{"Search" link finddeepsky_search} button to begin the search. @endnode @node finddeepsky_ic "IC Number" If "IC Number" is selected, you can find a @{"deep sky" link define.guide/deepsky} object by @{"IC number" link define.guide/ic}. Just type the IC number in the box provided and hit ENTER. A search request will be composed in the @{"Criteria" link finddeepsky_criteria} box. If it is acceptable, press the @{"Search" link finddeepsky_search} button to begin the search. @endnode @node finddeepsky_criteria "Criteria" This box performs two functions. If you enter a search request by using the @{"gadgets" link define.guide/gadget} above this box, the request will be composed and appear within. Alternately, you can enter a search criteria directly into this box if you use the proper entry format. You must press @{"Search" link finddeepsky_search} to get the computer to find the object of interest. @endnode @node finddeepsky_search "Search" After a search criteria has been composed and appears in the @{"Criteria" link finddeepsky_criteria} box (either automatically or manually), you must press the "Search" button to allow the computer to try and find the object of interest. @endnode @node window_findmiscobj "Miscellaneous Object Selection" This window allows you to find a miscellaneous object. Simply click on the object of interest and the software will center the object on the screen. If the object is too dim to show up with your current settings for @{"limiting magnitude" link define.guide/limitingmagnitude} in the @{"Display/Object Preferences" link window_display} window, the computer will zoom in until the object becomes visible. You will be allowed to choose from any objects appearing in the @{"Selected Objects" link misc_selected} list of the @{"Miscellaneous Objects" link window_miscobjs} window. @endnode @node window_animation "Animation Control Window" This window allows you to make user-definable animations. They are created and stored as "IFF ANIM5" files - the animation standard for Amiga computers. Many third party software packages can play these animations. The @{"showanim" link showanim} utility is provided for just that purpose. The @{"Lock Onto" link time_lockonto} @{"radio button" link define.guide/radiobutton} in the @{"Time Control" link window_time} window specifies what the animation should follow from frame to frame. You can tell "The Digital Universe" to keep its field of view fixed with respect to the horizon, follow the stars across the sky, or follow an object moving with respect to the stars. See the information provided on the "Time Control" window for further assistance. Several parameters of the animation may be specified to further customize it. As a few examples, you can create an animation which slowly zooms in on an area of sky, or shows how the sky's appearance changes as you move in a southerly direction across the Earth's surface. The possibilities are limited only by your own imagination. Help is available for the following @{"gadgets" link define.guide/gadget}: @{"Number of Frames" link animation_numframes} @{"Advance " link animation_advance} @{"Advance Units " link animation_advanceunits} @{"Right Ascension " link animation_ra} @{"Declination " link animation_dec} @{"Altitude " link animation_alt} @{"Azimuth " link animation_az} @{"Latitude " link animation_lat} @{"Longitude " link animation_long} @{"Field (ratio) " link animation_field} @{"Start " link animation_start} @endnode @node animation_numframes "Number of Frames" In this box, you can specify the number of frames of your animation. You cannot create an animation with less than 2 frames. @endnode @node animation_advance "Advance" This box, in conjunction with the @{"Advance Units" link animation_advanceunits} @{"gadget" link define.guide/gadget} to the right is used to tell the computer how much time should elapse between each frame. @endnode @node animation_advanceunits "Advance Units" This @{"gadget" link define.guide/gadget} is used in conjunction with the @{"Advance" link animation_advance} box to the left to tell the computer how much time should elapse between each frame. You can choose between the following units of time: seconds minutes hours days @{"Gregorian Years " link define.guide/gregorianyear} @{"Julian Years " link define.guide/julianyear} @{"Tropical Years " link define.guide/besselianyear} @{"Sidereal Years " link define.guide/siderealyear} @{"Anomalistic Years" link define.guide/anomalisticyear} @{"Eclipse Years " link define.guide/eclipseyear} @{"Gaussian Years " link define.guide/gaussianyear} @endnode @node animation_ra "Right Ascension" This box allows you to specify the value that should be added to the current @{"right ascension" link define.guide/rightascension} of the center of the field of view between frames. It should be specified in decimal hours. If you do not wish to advance the center of the field in right ascension, just leave the box blank. @endnode @node animation_dec "Declination" This box allows you to specify the value that should be added to the current @{"declination" link define.guide/declination} of the center of the field of view between frames. It should be specified in decimal degrees. If you do not wish to advance the center of the field in declination, just leave the box blank. @endnode @node animation_alt "Altitude" This box allows you to specify the value that should be added to the current @{"altitude" link define.guide/altitude} of the center of the field of view between frames. It should be specified in decimal degrees. If you do not wish to advance the center of the field in altitude, just leave the box blank. @endnode @node animation_az "Azimuth" This box allows you to specify the value that should be added to the current @{"azimuth" link define.guide/azimuth} of the center of the field of view between frames. It should be specified in decimal degrees. If you do not wish to advance the center of the field in azimuth, just leave the box blank. @endnode @node animation_lat "Latitude" This box allows you to specify the value that should be added to your current latitude between frames. It should be specified in decimal degrees. If you do not wish to change latitude throughout the animation, just leave the box empty. @endnode @node animation_long "Longitude" This box allows you to specify the value that should be added to your current longitude between frames. It should be specified in decimal degrees. If you do not wish to change longitude throughout the animation, just leave the box empty. @endnode @node animation_field "Field (ratio)" This box allows you to specify the value that should be multiplied to the current field of view between frames. If it is greater than one, the computer zooms out - if it is less than one, the computer zooms in. If you do not wish to zoom in or out throughout the animation, leave the value at 1.0. @endnode @node animation_start "Start Generating Animation" When you have the parameters of the animation all set up the way you like, press the "Start" button. The software will first bring up a requester asking where you would like to store the animation. By convention, animation files should end in a .anim extension. Then, the computer will begin to generate the animation. While "The Digital Universe" is calculating and drawing each frame of an animation, you will be unable to abort the process. However, while it is compressing the image into the animation file, you are given the opportunity to do so if you wish. When the animation has been completely generated, the software provides an icon with the file. Workbench users can simply double click on the icon to play back the animation (using @{"showanim" link showanim}, a utility provided with this package). @endnode @node window_report "Report Generation Window" This window allows you to generate numerical reports. They can be output to either a file or an attached printer. Each line in the report corresponds to a particular instant in time. Up to four columns of information may be generated per line. The information to be generated is selected using the lists in the center region of the window. The initial line of the report corresponds to the current time used by the software when report generation begins. More help is available for the following @{"gadgets" link define.guide/gadget}: @{"Advance " link report_advance} @{"Advance Units " link report_advanceunits} @{"Times " link report_times} @{"Type of Information" link report_category} @{"Particulars " link report_object} @{"Save Report to File" link report_save} @{"Print Report " link report_print} @{"View Report " link report_view} @endnode @node report_advance "Advance" This @{"gadget" link define.guide/gadget}, used in conjunction with the @{"Advance Units" link report_advanceunits} gadget to the right, allows the user to specify how much time is to elapse between lines of the report. @endnode @node report_advanceunits "Advance Units" This @{"gadget" link define.guide/gadget}, used in conjunction with the @{"Advance" link report_advance} gadget to the left, allows the user to specify how much time is to elapse between lines of the report. You can choose between the following units of time: seconds minutes hours days @{"Gregorian Years " link define.guide/gregorianyear} @{"Julian Years " link define.guide/julianyear} @{"Tropical Years " link define.guide/besselianyear} @{"Sidereal Years " link define.guide/siderealyear} @{"Anomalistic Years" link define.guide/anomalisticyear} @{"Eclipse Years " link define.guide/eclipseyear} @{"Gaussian Years " link define.guide/gaussianyear} @endnode @node report_times "Times" In this box, you can specify how often that time is to advance (ie: how many lines the report is to have). @endnode @node report_category "Type of Information" With these lists (one per column), you can tell the software what type of information you would like to generate. The entry you select with the mouse affects the data appearing in the @{"Particulars" link report_object} list below. @endnode @node report_object "Particulars" These lists (one per column) are used to specify the particulars of the @{"Type of Information" link report_category} selected in the list above. For example, if you pick "Apparent RA/Dec" in the "Type of Information" list, the "Particulars" list presents you with a list of objects for which the apparent @{"right ascension" link define.guide/rightascension} and @{"declination" link define.guide/declination} can be calculated. @endnode @node report_save "Save" If the user clicks on the "Save" button, a @{"requester" link define.guide/gadget} is brought up asking where he or she wishes to save the report. By default, all such reports should end in a .txt extension. When the user specifies the filename, report generation begins. @endnode @node report_print "Print" If the user clicks on the "Print" button, the report is generated and output to an attached printer, a line at a time. If you'd rather save the information to a file, press the @{"Save" link report_save} button instead. @endnode @node report_view "View" If the user clicks on the "View" button, the report is generated and output sent to the screen, in an Amigaguide window. @endnode @node window_searchht "Search Hypertext Files" This window allows the user to search through all the Amigaguide @{"hypertext" link define.guide/hypertext} files used with "The Digital Universe". You can search for a word, phrase or pattern. Additional help is available for the following @{"gadgets" link define.guide/gadget}: @{"Search String" link searchht_string} @{"Search " link searchht_search} @endnode @node searchht_string "Search String" You type the word, phrase, or pattern you are looking for in this box. The special characters used for pattern matches are displayed at the top of the window. As an example, suppose that you wanted to find all occurrences of "Halley", but were unsure of its spelling. If you know that it begins with an "Hal" and ends in a "y", you could instruct "The Digital Universe" to look for: Hal?*y It would then find all occurrences to "Halley" (as well as anything else that starts with an "Hal" and ends with a "y", including "halfway"). Searches are case-insensitive. It doesn't matter if you specify your search in upper or lower case letters. If you press the ENTER key after typing your search string, the software will automatically being to do its work, as if you'd hit the @{"Search" link searchht_search} button. @endnode @node searchht_search "Search" When you are done entering your search phrase in the @{"Search String" link searchht_string} @{"requester" link define.guide/gadget}, you can either press ENTER or the "Search" button to begin the search. There are approximately 1.5 megabytes of @{"hypertext" link define.guide/hypertext} provided with "The Digital Universe", so searching through it all can take a few moments. As it is searching, you are presented with the opportunity to abort your request. Once it has scanned through all the files, "The Digital Universe" displays a list with hypertext links to all the matches it found. @endnode @node window_printing "Printing Status" This window provides you with information on the status of your print job, including what the software is currently doing and how much percent of the request has been completed. It also provides the ability to stop the current print job in progress by pressing the "Abort" button. @endnode @node window_objectinfo "Object Information" If you click with the mouse pointer on an object on the screen, this window will tell you information about it. The precise details of what is displayed are highly dependent on the object itself, but definitions for most of the terms used appear in the online dictionary of astronomy (accessible by selecting "Dictionary" from the "Help" menu). Additional help is available for the following @{"gadgets" link define.guide/gadget}: @{"Print " link info_print} @{"More Info" link info_more} @endnode @node info_print "Print" This button allows the user to print a copy of the information in the window to an attached printer. The software assumes that the printer uses the ECMA-94 Latin 1 character set (conforms to ISO/DIS 6429.2 and ANSI X3.64-1979 standards) for foreign language and special characters. This is the same character set used by the Amiga for screen text. If it does not use this standard, you may see inappropriate representations of characters like the degree symbol. @endnode @node info_more "More Info" If this button is not "ghosted" (if is able to be depressed), more information is available for the object. By pressing the button, an Amigaguide @{"hypertext" link define.guide/hypertext} window is displayed which may contain audiovisual information in addition to regular text. @endnode @node window_calculating "Calculating..." This window appears when "The Digital Universe" has spent more than a few seconds calculating something. If you press the "Abort" button on the window, you can tell the software to stop the calculation in progress. Be aware that it may take a few seconds to regain control of the computer, however. @endnode @node window_editobject "Miscellaneous Object Orbit Entry" This window allows you to enter or change @{"orbital elements" link define.guide/orbitalelements} for comets or asteroids. In addition, it also allows you to specify locations for user-defined fixed objects. Ensure that you only edit or add items to the "misc.uof" file! The window appears when you press @{"Edit" link misc_edit} or @{"Add" link misc_add} on the @{"Miscellaneous Objects" link window_miscobjs} window. Additional help is available for the following @{"gadgets" link define.guide/gadget}: @{"Primary Name " link edit_primaryname} @{"Secondary Name " link edit_secondaryname} @{"Object Type " link edit_objecttype} @{"Perihelion Date " link edit_perihelion} @{"Perihelion Distance " link edit_distance} @{"Eccentricity " link edit_eccentricity} @{"Argument of Perihelion " link edit_argument} @{"Long. of Ascend. Node/RA" link edit_node} @{"Inclination/Dec " link edit_inclination} @{"Mag param. 1 " link edit_mag1} @{"Mag param. 2 " link edit_mag2} @{"Mag param. 3 " link edit_mag3} @{"Mag param. 4 " link edit_mag4} @{"Save " link edit_save} @endnode @node edit_primaryname "Primary Name" This @{"requester" link define.guide/gadget} allows you to specify the primary name of the object. @endnode @node edit_secondaryname "Secondary Name" This @{"requester" link define.guide/gadget} allows you to specify a secondary name for an object. @endnode @node edit_objecttype "Object Type" These @{"radio buttons" link define.guide/radiobutton} specify the type of object being defined. @endnode @node edit_perihelion "Perihelion Date" This @{"requester" link define.guide/gadget} allows you to define the @{"perihelion" link define.guide/perihelion} date for the object. It is often designated by the symbol "T". "The Digital Universe" expects the perihelion date to be given in the format yyyy/mm/dd.d. If you are not given the perihelion date, you may be able to calculate it from other data. See @{"Calculating Missing Orbital Elements" link calculatingmissing} for further details. @endnode @node edit_distance "Perihelion Distance" You can use this @{"requester" link define.guide/gadget} to specify the distance in @{"AU" link define.guide/au} from the object to the Sun when it is at @{"perihelion" link define.guide/perihelion}. It is usually designated by the symbol "q". If you are not given the perihelion distance, you may be able to calculate it from other data. See @{"Calculating Missing Orbital Elements" link calculatingmissing} for further details. A perihelion distance of 0 has a special meaning to "The Digital Universe". In this circumstance, the object is taken to be fixed in the sky. The @{"right ascension" link define.guide/rightascension} of the object is to be specified in the @{"Long. of Ascend. Node/RA" link edit_node} requester and the @{"declination" link define.guide/declination} in @{"Inclination/Dec" link edit_inclination}. In addition, the @{"magnitude" link define.guide/magnitude} should be entered into @{"Mag param. 1" link edit_mag1}. @endnode @node edit_eccentricity "Eccentricity" The @{"eccentricity" link define.guide/eccentricity} of the object's orbit should be entered into this @{"requester" link define.guide/gadget}. It is usually represented by the symbol "e". @endnode @node edit_argument "Argument of Perihelion" The argument of perihelion (usually denoted by the lower case Greek letter "omega") should be entered into this @{"requester" link define.guide/gadget}. If it is not supplied, you may be able to calculate it from information provided in the section entitled @{"Calculating Missing Orbital Elements" link calculatingmissing}. @endnode @node edit_node "Long. of Ascend. Node/RA" One of two pieces of information can be found in this @{"requester" link define.guide/gadget}. If an asteroid or comet is being defined, it will contain the longitude of the ascending node. If a stationary object is being defined (by setting the @{"Perihelion Distance" link edit_distance} to 0), it should contain the @{"right ascension" link define.guide/rightascension} of the object. The Longitude of the Ascending Node is usually represented by the upper case Greek letter "omega", and the right ascension by "alpha". @endnode @node edit_inclination "Inclination/Dec" One of two pieces of information can be found in this @{"requester" link define.guide/gadget}. If an asteroid or comet is being defined, it will contain the @{"inclination" link define.guide/inclination} of the orbit. If a stationary orject is being defined (by setting the @{"Perihelion Distance" link edit_distance} to 0), it should contain the @{"declination" link define.guide/declination} of the object. The inclination is usually represented by the letter "i", and the declination by the Greek letter "delta". @endnode @node edit_mag1 "Mag param. 1" The value in this box may represent one of several different things depending on what type of object is being defined. If the object is stationary (defined by setting the @{"Perihelion Distance" link edit_distance} to 0), it simply represents the @{"magnitude" link define.guide/magnitude} of the object. If the object being defined is a comet, it represents a brightness parameter designated H(1,0) of the coma. If the object is an asteroid, it represents a parameter designated "H". @endnode @node edit_mag2 "Mag param. 2" The value in this box may represent one of two different things depending on what type of object is being defined. If the object is a comet, it represents a brightness parameter designated as "n" for the coma. If the object is an asteroid, it represents a parameter designated "G". @endnode @node edit_mag3 "Mag param. 3" This @{"requester" link define.guide/gadget} only has meaning for comets. It represents a brightness parameter designated H(1,0) of the nucleus. @endnode @node edit_mag4 "Mag param. 4" This @{"requester" link define.guide/gadget} only has meaning for comets. It represents a brightness parameter designated "n" of the nucleus. @endnode @node edit_save "Save" If this button is depressed, the updated @{"orbital elements" link define.guide/orbitalelements} are written to the orbit file. You will have to double click on the entry in the @{"Objects in the File" link misc_filelist} list in order to make it appear on the @{"Selected Objects" link misc_selected} list if you want "The Digital Universe" to determine where the new object is. @endnode @node calculatingmissing "Calculating Missing Orbital Elements" The orbit of an object can be specified in a wide variety of different ways. Sometimes you will be given @{"orbital elements" link define.guide/orbitalelements} which may not correspond directly to the elements required by "The Digital Universe". If this is the case, you may be able to calculate the missing quantities by using the some of the relations given below: a = semimajor axis, in @{"AU" link define.guide/au} e = @{"eccentricity" link define.guide/eccentricity} q = @{"perihelion" link define.guide/perihelion} distance, in AU n = mean motion, in degrees/day. T = @{"Julian Date" link define.guide/juliandate} of perihelion t = Julian Date of @{"epoch" link define.guide/epoch} M = mean anomaly omega = argument of perihelion Omega = longitude of the ascending node pi = longitude of perihelion L = mean longitude of the object q a = ----- 1-e 0.9856076686 n = ------------ a*sqrt(a) -M if (M<180) T = --- + t n 360-M else T = ----- + t n omega = pi - Omega M = L - omega - Omega @endnode @node faq "Frequently Asked Questions" Though "The Digital Universe" is intended to be quite user-friendly, there are periodically circumstances where people may become confused with its operation. This short section contains answers to a few frequently asked questions. @{"Question 1" link question1}: Periodically I see quantities expressed as numbers separated by colons (such as 21:45:42). What does this mean? @{"Question 2" link question2}: What settings should I give the software to get the most accurate results? @{"Question 3" link question3}: What settings should I give the software to get results the quickest? @{"Question 4" link question4}: I'm trying to make an animation while zoomed in close to a planet, but it keeps moving off the screen. What's wrong? @{"Question 5" link question5}: Why am I unable to select some menu items or @{"gadgets" link define.guide/gadget}? @{"Question 6" link question6}: What is the difference between Planetarium and Local Mode, and when should I use one or the other? @{"Question 7" link question7}: I would like to see where a particular comet (or asteroid, or Earth-orbiting satellite) is, but the procedure seems a bit complicated. @{"Question 8" link question8}: I'm using the menu to try and open a window but nothing is appearing. What's wrong? @{"Question 9" link question9}: On some (but not all) windows, the font is much too small to be read. Why is this, and what should be done? @{"Question 10" link question10}: When I generate an animation, the first frame looks like it doesn't belong. What's causing this? @{"Question 11" link question11}: When I open up the @{"Time Control" link window_time} window, I'm presented with ten different boxes where I can enter the time. Where should I enter it? @{"Question 12" link question12}: When I click on an object, I see that the rise and set times are "Unavailable". How can I see what they are? @endnode @node question1 "Question 1" Periodically I see quantities expressed as numbers separated by colons (such as 21:45:42.1). What does this mean? Astronomers often deal with angular measurements. For example, they may need to know how many degrees above the horizon an object is, or how large an object appears to be. Though they can specify these measurements in decimal notation (21.7617 degrees), this is not commonly done. Normally, a measurement system called "degree-minute-second" is used to deal with fractional degrees. In this system, there are 60 minutes in a degree and 60 seconds in a minute. Thus, 21.7617 degrees can be expressed as 21 degrees, 45 minutes, and 42.1 seconds. Though it may seem a bit needlessly confusing, it is not without precedent. After all, we have been dividing the hour up into minutes and seconds in the same manner for centuries. The "official" notation for such a quantity would be written as 21°45'42".1 (where in actuality the " symbol would appear directly above the decimal point, not in front of it). However, this notation is somewhat cumbersome to enter on a standard keyboard. To simplify the process, the scheme of using colons (:) to separate the various quantities has been "unofficially" adopted by "The Digital Universe". Thus, the quantity may be expressed as 21:45:42.1. The user must decide whether a quantity expressed like this refers to an angular measurement or a measurement of time by context. @endnode @node question2 "Question 2" What settings should I give the software to get the most accurate results? If you are interested in obtaining the highly accurate results that "The Digital Universe" is capable of generating, there are several parameters that you should manipulate. Naturally, the more that the computer has to consider, the slower it will become. Therefore, unless you have an extremely fast Amiga it is not recommended that you leave these parameters set for everyday use. In the @{"Display/Object Preferences" link window_display} window, set all of the options under "Precision" - namely @{"precession" link define.guide/precession}, @{"proper motion" link define.guide/propermotion}, @{"nutation" link define.guide/nutation}, @{"aberration" link define.guide/aberration}, and @{"refraction" link define.guide/refraction}. If you are interested in obtaining rise and set time information for objects, ensure that you unselect @{"Fast info" link display_fastinfo}. Click on @{"Use" link display_use} or @{"Save" link display_save}. Then, open up the @{"Time Control" link window_time} window and enter "DATE" in the box marked @{"Epoch" link time_epoch} before pressing @{"Use" link time_use}. Once this has all been accomplished, "The Digital Universe" will provide the most accurate calculations it is capable of, at the expense of taking longer to do so. @endnode @node question3 "Question 3" What settings should I give the software to get results the quickest? "The Digital Universe" was originally designed to provide the most accurate astronomical calculations generally available to the owner of a personal computer. As such, it may be slower than some competing products. To some extent, the user can tell the computer to ignore some effects it would otherwise consider, speeding up calculations and screen updates. Of course, the results will not be as accurate, but they may be acceptable for most everyday use. In the @{"Display/Object Preferences" link window_display} window, unselect all of the options under "Precision" - namely @{"precession" link define.guide/precession}, @{"proper motion" link define.guide/propermotion}, @{"nutation" link define.guide/nutation}, @{"aberration" link define.guide/aberration}, and @{"refraction" link define.guide/refraction}. If you are not interested in obtaining rise and set time information for objects, ensure that you select @{"Fast info" link display_fastinfo}. Selecting @{"Fast Labels" link display_fastlabels} as well will reduce the amount of time the software requires to label objects on the screen. Click on @{"Use" link display_use} or @{"Save" link display_save}. Then, open up the @{"Time Control" link window_time} window and enter "J2000" in the box marked @{"Epoch" link time_epoch} before pressing @{"Use" link time_use}. Once this has all been accomplished, "The Digital Universe" will require less time in performing its calculations, at the expense of a loss of accuracy. @endnode @node question4 "Question 4" I'm trying to make an animation while zoomed in close to a planet, but it keeps moving off the screen. What's wrong? When making an animation, the computer needs to be told what it should be following between frames. When you first start "The Digital Universe", it assumes that it should follow the stars across the sky. But since planets move with respect to the stars, it won't be too long before the planet has moved out of your field of view. To get the software to lock onto a planet or other object during an animation, open up the @{"Time Control" link window_time} window, and bring up the "Time Advancement" section. With the @{"Lock Onto" link time_lockonto} @{"radio buttons" link define.guide/radiobutton}, select "Object". Then, click on the object you wish to follow in the list to the right. After pressing @{"Use" link time_use} at the bottom of the window, you should then be able to generate your animation and automatically follow the planet as it moves. @endnode @node question5 "Question 5" Why am I unable to select some menu items or @{"gadgets" link define.guide/gadget}? If you are unable to select one of these objects, chances are that it is "ghosted" (shaded out). Sometimes some options do not make sense unless other options are set. For example, if you use the menu to open up the @{"Time Control" link window_time} window, it cannot be opened up a second time. As a result, the menu item becomes ghosted while the window remains open. As another example, it does not make sense to label @{"deep sky" link define.guide/deepsky} objects or search for these objects if they are not being displayed on the screen. To enable a "ghosted" option, you just have to change the status of whatever is causing it to be "ghosted". There are too many dependencies like this throughout the program to list in detail, but most of them should be fairly straightforward to discover. @endnode @node question6 "Question 6" What is the difference between Planetarium and Local mode, and when should I use one or the other? Planetarium and Local mode merely differ in the orientation they give to the appearance of the sky. Local mode draws the sky as it appears from your location on Earth. Up is up and left is left. For most people just beginning to develop an interest in astronomy, this way of viewing the sky is the most natural. But the orientation and appearance of the night sky is highly dependent on the time and geographical position of the observer. As a result, astronomers have developed a "standard" way of representing the sky, similar to the way terrestrial maps have been defined. In this representation, up is the direction towards the north @{"celestial pole" link define.guide/celestialpoles}. To the left is east (opposite to a terrestrial map since instead of looking down upon the Earth, we're looking up into the sky). If Planetarium Mode is selected, "The Digital Universe" will orient the display in this manner. This enables the user to generate star maps appearing like those published in printed star atlases. If you are generating an animation of a planet's rotation about its axis, you should be in Planetarium mode. Otherwise, in addition to the planet's rotation, you will see it "wobble" back and forth. This apparent motion isn't something the planet actually does, but results from the planet's changing orientation with respect to the user's horizon throughout the day. @endnode @node question7 "Question 7" I would like to see where a particular comet (or asteroid, or Earth-orbiting satellite) is, but the procedure seems a bit complicated. The procedure is a bit complicated since "The Digital Universe" contains information on tens of thousands of these objects. If it were to figure out where each and every one was located, it would take a very long time to do so. Therefore, you must first select which of these "miscellaneous objects" you want "The Digital Universe" to consider. First, open up the @{"Miscellaneous Objects" link window_miscobjs} window and choose the objects you are interested in, ensuring that they appear in your @{"Selected Objects" link misc_selected} list. For more information on this process, see the help for the "Miscellaneous Objects" window. Then, close the window (or optionally @{"Save" link misc_save} your preferences to disk so that they remain in effect the next time you start the software). Open up the @{"Display/Object Preferences" link window_display} window and ensure that you have told the computer to plot miscellaneous objects (by selecting the @{"Misc. Object" link display_miscobject} @{"gadget" link define.guide/gadget} in the "Objects" section of "Calculation & Display"). It wouldn't hurt to pick @{"Misc. Object Names" link display_miscobjectnames} under "Object Preferences" on this window either, to label the object. Then, the computer should be calculating and plotting the position of the object you're interested in. You can find the object of interest from the "FIND" menu if it doesn't appear on your screen. @endnode @node question8 "Question 8" I'm using the menu to try and open a window but nothing is appearing. What's wrong? First, make sure the menu option is not "ghosted" (shaded out). If it is, then the option is not currently available. See @{"Question 5" link question5} for more information. If the window should be appearing but isn't, there are two possible explanations. You may be out of chip (graphics) memory. Every window opening on the screen takes a certain amount of chip memory. If you have too many windows open, or your graphics memory has become too fragmented, it is possible that not enough memory remains to open the new window. Either try closing some windows or exit from "The Digital Universe" and reboot the computer to unfragment the memory and try again. Another possibility, if you are using a non-interlaced screen, is that the windows are too big to fit on the screen. They should all be able to fit on a 640 X 200 screen if you have selected @{"Topaz Font" link screen_usetopaz} in the @{"Setting Screen Mode" link window_screenmode} window. Ensure that it has been selected. @endnode @node question9 "Question 9" On some (but not all) windows, the font is much too small to be read. Why is this, and what should be done? If you find this occurring, you are probably using a screen that is too small to fit the windows properly. If you are running a 640 X 200 screen, make sure that you have selected @{"Topaz Font" link screen_usetopaz} in the @{"Setting Screen Mode" link window_screenmode} window. @endnode @node question10 "Question 10" When I generate an animation, the first frame looks like it doesn't belong. What's causing this? When an animation is made, the initial frame is always a copy of the screen at the instant you press @{"Start" link animation_start} - it doesn't recalculate and redraw the screen first. If you have specified that the computer should lock onto a particular object (in the @{"Time Control" link window_time} window), the software will follow this object throughout the animation. But if the object is not centered on the screen before the animation starts, the first frame will not "belong" with the rest. To avoid this problem, choose @{"Recalculate" link menu_recalculate} from the "Project" menu immediately before generating the animation. This will ensure that the software centers the field of view on whatever is being locked onto before the animation begins. This step should only be necessary if you are locked onto an object and have manually changed your field of view since you left the "Time Control" window. @endnode @node question11 "Question 11" When I open up the @{"Time Control" link window_time} window, I'm presented with ten different boxes where I can enter the time. Where should I enter it? For full details on what all these boxes mean, refer to the help given for the "Time Control" window itself. For those who just want to see what the sky will look like at 10:00 pm tonight without worrying about all the other details, just enter your local time into the top left box (Conventional Local Mean Time). Remember that you have to enter the time in 24 hour format (in this case, 10:00 pm is entered as 22:00), that you need the date as well as the time, and that you must press ENTER when you are done. Provided that you have set up your @{"Time Zone" link environ_timezones} properly in the @{"Setting Environment Parameters" link window_environ} window, when you click on the @{"Use" link time_use} button, the software should show you a view of the sky for the time you specified. @endnode @node question12 "Question 12" When I click on an object, I see that the rise and set times are "Unavailable". How can I see what they are? For objects which move with respect to the background stars (such as planets), a computation of the rise and set times is a rather complicated procedure. On some computers, this may slow down the speed at which the @{"Object Information" link window_objectinfo} window appears to unacceptable levels, particularly when such information is not required. The user is therefore given the option of whether or not to display rise and set times with object information. To allow the computer to calculate these times, unselect the @{"Fast Info" link display_fastinfo} button in the @{"Display/Object Preferences" link window_display} window and press @{"Use" link display_use} or @{"Save" link display_save}. Note that the times for different phases of the Moon are also marked as being unavailable if this option is selected. @endnode @node kbmouse "Keyboard and Mouse Operations" You should already be familiar with using the mouse to select items from the menu bar and click on @{"gadgets" link define.guide/gadget}, as well as using the keyboard to enter information. However, there are a few ways that you can use the keyboard and mouse to control the operation of "The Digital Universe" that may not be as obvious. @{"Mouse Operations " link mouse} @{"Keyboard Operations" link keyboard} @{"Combined Operations" link combined} @endnode @node mouse "Mouse Operations" There are two things that you can do with the mouse in addition to clicking on @{"gadgets" link define.guide/gadget} and menu items. 1. If you click on a star, planet, or other object on the screen, a window will appear with information about the object. 2. If you click and hold down the left mouse button and move the mouse you will drag out a "zoom box". When the mouse button is released, the screen will zoom in to show those objects which were enclosed by the box. Since it is impossible to accurately portray the @{"celestial sphere" link define.guide/celestialsphere} on a flat computer monitor, distortion will occur near the edges of the screen. It is at its strongest when large fields of view are being displayed. The "zoom box" will distort itself to more accurately indicate which objects will be displayed on the screen when the mouse button is released. If you zoom in sufficiently close to a planet or moon, the appearance of the object's disk will be generated. Maps of Venus, the Moon, Mars, Jupiter, and Saturn are provided with the software to provide a realistic view of the object. These maps will be used if @{"Features & Flattening" link display_features} has been enabled on the @{"Display/Object Preferences" link window_display} window. @endnode @node keyboard "Keyboard Operations" There are several things which can be done directly from the keyboard to control the operation of "The Digital Universe". 1. Menu shortcuts - beside most menu options you will find a stylized "A" followed by a letter or symbol. This indicates a method of choosing the menu item without using the mouse. Just hold down the right Amiga key (to the right of the spacebar) and press the letter or symbol indicated. 2. Gadget shortcuts - some @{"gadgets" link define.guide/gadget} have one of the characters in their labels underlined. If the window containing the gadget is currently active and you type the underlined letter, the gadget itself will become active. In this manner, you do not have to choose a gadget to type in with the mouse. 3. Tab cycling - if you press the TAB key (to the left of the 'Q' key) when a window with multiple gadgets is active, you will cycle through making the various gadgets active. If you hold down the SHIFT key while typing the TAB key, the gadgets will cycle in the reverse order. 4. Escape key - if you press the escape key (marked ESC) while a window is active, the window will be closed. 5. Number keys - if the background window (the window upon which all the stars are drawn) is active, you can press one of the number keys (above the standard keyboard) to instantly zoom to one of the fields of view that you preset in the @{"Field of View Preferences" link window_fields} window. 6. Numeric keypad - on most models of Amiga, the numeric keypad is located to the right of the standard keyboard. If the background window is active and you press one of the keys numbered 1, 2, 3, 4, 6, 7, 8, or 9 the screen will pan in the appropriate direction. If 5 is pressed, the field of view will zoom out by a factor of 1.5, and if the decimal point (.) on the numeric keypad is pressed, the field will zoom in by a factor of 1.5. 6. Arrow keys - If the background window is selected and you press the right arrow key, the time will be advanced by the amount specified in the @{"Time Control" link window_time} window for manual advancement. Likewise, if you press the left arrow key, the time used by the software will be decreased by the same amount. 7. HELP key - if you press the HELP key while the background window is active, you will receive online help for "The Digital Universe". If you depress this key while the mouse pointer is above some @{"gadget" link define.guide/gadget} or window, information about the use of the gadget or window will be displayed. @endnode @node combined "Combined Operations" There are two operations which can be done through a combined use of the mouse and keyboard. 1. If you hold down the SHIFT key while clicking at a spot on the screen, the software will center this location in your field of view. 2. If you hold down the Control key (marked CTRL) while dragging with the mouse (moving the mouse with the left mouse button depressed) you will drag out a line that can be used to measure the distance between two points. When the mouse button is released, the angular distance between these points will be displayed. @endnode @node configuration "Configuration of the software" Other than the configuration options available from the @{"Setting Screen Mode" link window_screenmode}, @{"Setting Environment Parameters" link window_environ}, and @{"Display/Object Preferences" link window_display} windows, there are a few additional things that you can configure with the operation of "The Digital Universe". When viewing @{"hypertext" link define.guide/hypertext}, you will periodically come across links to pictures or audio samples. "The Digital Universe" calls the scripts named "playsound" and "showpic" in the DU: directory to deal with these files. The scripts are currently configured to use software programs called @{"DUAudio" link duaudio} and @{"ShowAnim" link showanim}, supplied with the package, but if you have software that you would rather use, you only need to modify these scripts with a text editor. @endnode @node startdu "Starting The Digital Universe" If you would like to start "The Digital Universe" from the Workbench, you only have to double click upon the "DigitalUniverse" icon once the software has been installed from disk. The introduction sequence to "The Digital Universe" may crash on some Amigas with 3rd party graphics boards. If this is the case with your machine, or you would merely like to run the software without seeing the introduction, just double click on the "DigitalUniverseNoIntro" icon instead. On the other hand, if you would rather start the software from the command line (CLI), first ensure that you are using a stack of at least 6000 bytes. Type 'stack' at the CLI prompt if you are not sure. If you need to raise the stack, just type 'stack 6000'. Refer to your AmigaDOS manual for more information on the 'stack' command. Once this is done, change to the DU: directory and type: DigitalUniverse If you would like to avoid the introduction, type: DigitalUniverse nointro One other option is available to CLI users. If your configuration somehow becomes corrupted or you would like to return your settings to the factory defaults, type: DigitalUniverse init Remember that if you do so, all your previous settings will be lost. When you run the software for the first time, or after you have returned the settings to factory defaults, you should tell it where on the Earth you are located, and what time zone you are in. This can be done by choosing @{"Environment Prefs" link menu_environ} from the menu bar, to bring up the @{"Setting Environment Parameters" link window_environ} window. See the help associated with this window for more details. @endnode @node utilities "Utilities - other software provided with the package" This information is not provided with the demonstration version of "The Digital Universe". Please consult @{"Ordering The Digital Universe" link ordering} for more information on how to obtain a registered version. @endnode @node showanim "ShowAnim" This information is not provided with the demonstration version of "The Digital Universe". Please consult @{"Ordering The Digital Universe" link ordering} for more information on how to obtain a registered version. @endnode @node duaudio "DUAudio" This information is not provided with the demonstration version of "The Digital Universe". Please consult @{"Ordering The Digital Universe" link ordering} for more information on how to obtain a registered version. @endnode @node jahnprecise2uof "jahnprecise2uof" This information is not provided with the demonstration version of "The Digital Universe". Please consult @{"Ordering The Digital Universe" link ordering} for more information on how to obtain a registered version. @endnode @node jahnsingle2uof "jahnsingle2uof" This information is not provided with the demonstration version of "The Digital Universe". Please consult @{"Ordering The Digital Universe" link ordering} for more information on how to obtain a registered version. @endnode @node jahnnumber2uof "jahnnumber2uof" This information is not provided with the demonstration version of "The Digital Universe". Please consult @{"Ordering The Digital Universe" link ordering} for more information on how to obtain a registered version. @endnode @node jahncomet2uof "jahncomet2uof" This information is not provided with the demonstration version of "The Digital Universe". Please consult @{"Ordering The Digital Universe" link ordering} for more information on how to obtain a registered version. @endnode @node tle2uof "tle2uof" This information is not provided with the demonstration version of "The Digital Universe". Please consult @{"Ordering The Digital Universe" link ordering} for more information on how to obtain a registered version. @endnode @node ordering "Ordering The Digital Universe" This demonstration version of "The Digital Universe" has several disabled features (such as only displaying the stars in one small region of the sky, not allowing you to advance the time past December 31, 1995, and providing only a small portion of the hypertext encyclopedia of astronomy). By ordering the registered version of this software, these restrictions will be removed. There are two packages which may be of interest to the amateur astronomer. First and foremost is "The Digital Universe" software itself, which comes provided with a 138 page user manual. Secondly, in the process of creating the package, more than 700 pages of a hypertext multimedia encyclopedia was created (the electronic version of which is shipped with the software). However, since many individuals prefer reading from paper than the computer screen, a printed version of this information is also available. The prices of "The Digital Universe" software and printed encyclopedia (as of November 1, 1995) can be found in the following table. All prices include shipping and handling, and Canadian prices include 7% GST. Note that the prices for Canadian orders are quoted in Canadian dollars, UK orders are quoted in British pounds, and US and other international orders are quoted in US dollars. If you are an educational user, or a member of an Amiga user group, you qualify for a 15% reduction in the prices appearing below. Contact us for further details. Prices and promotions are subject to change without notice. Canada (CAN $) US (US $)* UK (pounds)* Inter.(US $)* -------------- ------------ ------------ ------------- Software 149.95 129.95 89.95 139.95 Encyclopedia 69.95 64.95 47.95 74.95 *NOTE: Since we must process all credit card transactions in Canadian dollars, the US, UK, and international prices provided above should only be considered as an estimate if you are using a credit card for payment. Due to exchange rate fluctuations between the time of purchase and the time your credit card company processes the transaction, the actual amount may be a few dollars more or less than that quoted above. However, the prices will be accurate for cheque or money order transactions. Payment can be made by check (drawn in Canadian dollars, US dollars, or British pounds), money order, Visa, or Mastercard. We need to know your name and address for the registration, and the shipping address (if different). In addition, if you are paying by Visa or Mastercard, the cardholder's name, credit card number, and expiry date are required. See the file entitled "ProductInfo", included with this archive, for more information (such as system requirements) and a sample order form. Orders may be sent to: Syzygy Research & Technology Ltd. Box 75 Legal, AB T0G 1L0 CANADA Phone: (403) 961-2213 Internet email: sales@syz.com or you can visit our WWW site with the following URL: http://www.syz.com @endnode @node productinfo "The Digital Universe - product information" PRODUCT DESCRIPTION ------------------- "The Digital Universe" is a complete astronomy program for the amateur or professional observer. It combines the advantages of traditional "planetarium" programs with a massive hypertext multimedia encyclopedia to create an effective tool which assists the user in observing and learning about the heavens. 50,000 lines of code, more than 700 pages of hypertext, and thousands of man-hours have gone into this product to make it the most complete program of its class. The software would not have been possible without the generous assistance of countless individuals from the Canadian Space Agency, the National Research Council of Canada, NASA, JPL, NORAD, the European Space Agency, the Bureau des Longitudes, the Smithsonian Astrophysical Observatory, the Russian Academy of Sciences, and several other organizations worldwide. PRODUCT FEATURES ---------------- The following features by no means summarize all the things which the software is capable of. Due to space considerations, only the major features can be summarized here. - The following databases are integrated into the software: 1. Yale Bright Star (YBS) Catalogue of 9110 stars. 2. Smithsonian Astrophysical Observatory (SAO) Catalogue of over 250,000 stars. 3. Messier's Catalogue of 110 deep sky objects (galaxies, nebulae, and clusters). 4. Sky & Telescope's NGC 2000.0 Catalogue of 13,226 deep sky objects. 5. Tom Lorenzin's "1000+" database of observing comments for over 2000 objects. 6. Jost Jahn's comet database containing 2298 cometary orbits. 7. Jost Jahn's minor planet database containing orbital information for thousands of asteroids. 8. Ted Molczan's and T. S. Kelso's orbital information for approximately 900 Earth-orbiting satellites. - The software can generate accurate views of the night sky for any date from 100,000 BC to 100,000 AD. - The package includes over 700 pages of hypertext, including an introduction to astronomy, dictionary of terms, biographies of famous people, celestial object descriptions, and summaries of every interplanetary spacecraft launched to date. - More than 250 pictures are linked into the hypertext encyclopedia. They include images of all the planets, most of their satellites, all of the Messier objects, some NGC objects, and many miscellaneous images. A few audio clips are incorporated as well. - A context-sensitive help system, linked into the online encyclopedia, is integrated into the software. - The user can select whether or not they want to consider effects such as precession, proper motion, nutation, aberration, or refraction. - "The Digital Universe" uses the latest analytic theories of motion for the planets (VSOP87) and their satellites, resulting in typical accuracies of better than 1 arcsecond (1/3600th of a degree). - The current analytic theory of motion for the moon (ELP2000-85) has been extended to improve its accuracy even further for times within a few hundred years of the present. The extension was done specifically for "The Digital Universe". - NORAD's SGP4 model of orbital motion is used to accurately predict the apparent positions and movement of Earth-orbiting satellites. "The Digital Universe" can work with standard "2-line" orbit files. Hundreds of satellites are included with the software, and information is provided to explain how to obtain future data sets as new satellites are launched and older orbits decay. - Unlike many other astronomy programs which only consider the four brightest satellites of Jupiter, "The Digital Universe" accurately computes orbits for the moons of: Earth: Our Moon Mars: Phobos and Deimos Jupiter: Io, Europa, Ganymede, Callisto, Amalthea, and Thebe Saturn: Mimas, Enceladus, Tethys, Dione, Rhea, Titan, Hyperion, Iapetus, Phoebe, Telesto, Calypso, and Helene Uranus: Miranda, Ariel, Umbriel, Titania, and Oberon Neptune: Triton and Nereid Pluto: Charon When the software is zoomed in sufficiently to the planet of interest, the moons are rendered in their proper positions. - When zoomed in to most planets and satellites, the object's orientation and phase is determined and a latitude/longitude grid superimposed if the user desires. Maps of Venus, the Moon, Mars, Jupiter, and Saturn are incorporated into the software to generate accurate renditions of the appearance of these objects. The ring systems of Saturn and Uranus are rendered. - Supports the Amiga preferences printer. Plots of star charts, etc. are far more than a simple screen dump. The maximum resolution of the printer is used for outstanding clarity. - The user can enter his or her own horizon, if desired. Horizons for multiple observing sites can be configured. - The user can select their location from a list of over 1000 cities, or enter their latitude, longitude, and altitude above sea level manually if higher accuracy is desired. - Completely configurable IFF animations can be generated. To mention just two examples from the infinite number of possibilities, you can see how stars move and constellations distort over centuries, or view how Saturn's rings change their orientation and appearance over time. "The Digital Universe" can also save screen snapshots as ILBMs. - A report generation feature lets you choose between a wide variety of data and customize tabular reports. They may either be printed or saved to disk. - Provided that you have sufficient chip memory, the screen upon which "The Digital Universe" runs can be of any size. If the screen is larger that can fit on the monitor, you can scroll around simply by moving your mouse to the edge of the visible area. A screenmode requester is provided to allow users to specify their particular monitor. - All development was done entirely on Amiga. It is not a port from the IBM or Macintosh world. As a result, the software closely adheres to the Amiga style guidelines and behaves in the manner you would expect from Amiga software. SYSTEM REQUIREMENTS ------------------- The software will run on any Amiga with Workbench 2.04 or greater, at least 3 megabytes of memory, and a minimum of 11 megabytes of hard drive space (17 megabytes of hard drive space is required for a full installation). Due to the calculation-intensive nature of this software, an accelerated Amiga and math chip (FPU) is strongly recommended, though not required. See also: @{"Ordering The Digital Universe" link ordering}. @endnode