The Starbase One Astronomy & Space Collection

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Text File | 1990-01-10 | 17.3 KB | 362 lines

SILICON SKY Version 2.6 Larry Adkins I. Introduction SILICON SKY is an interactive astronomy program which displays a quite realistic representation of the sky as seen from any latitude on earth for any date and looking in any direction. The program will display the location of the sun, moon and planets and will show the correct phase of the moon. Finally, it identifies the constellations visible on the screen by marking out their boundaries. It is most impressive with an EGA graphics system, but it can be configured for CGA using the Setup initialization program. Instructions for use are given in the following sections. This version (2.6) is the third release of the program. The main new feature beyond version 2.0 is the addition of graphic displays of the five naked eye planets. Here you can see the phases of Mercury and Venus, the surface markings on Mars, the satellites of Jupiter, and the orientation of Saturn's rings. The data accompanying the graphics give rise and set times, the distance of the planets from the earth and the apparent size of the planets. II. Setup and Initialization SILICON SKY should work on any IBM or IBM compatible with either a color graphics (CGA) or an enhanced graphics (EGA) adaptor card. However, you must first do two things: (1) Un-archive the main program (SKY.EXE), and (2) Customize the program for your locality The main program has been archived into the file named SKY.EXE so that all necessary files will fit on one 360K disk. The main program can be extracted simply by typing "SKY" and hitting return. However, the reason for archiving in the first place is because everything will not fit on the disk. Thus the program must be copied either to a hard disk, a high density floppy, or some non-critical files must be deleted from the 360K disk. The following procedures are recommended: FIRST: MAKE A BACKUP OF THE ORIGINAL AND STORE IT IN A SAFE PLACE IF YOU HAVE A HARD DISK: 1. Make a directory (MD SISKY) and copy the contents of the disk into this directory. 2. Go to the directory, type "SKY" and hit return. 3. This extracts the main program file named "SISKY.EXE" and the program is ready to run either by typing "SISKY" RETURN or "GO" RETURN. IF YOU ARE RUNNING FROM 360K FLOPPIES: 1. Copy SKY.EXE, SETUP.EXE, and READ.ME onto a fresh disk. 2. Go to the new disk, type "SKY" and hit RETURN. This will extract the main program file SISKY.EXE and place it on the new disk. 3. Delete SKY.EXE, READ.ME and SETUP.EXE from the OLD disk. 4. Copy SISKY.EXE from the NEW disk to the OLD disk (the disk will now hold SISKY.EXE since sufficient space has been made available by deleting the files listed above.) Of course, if you have a 1.2M or 1.4M floppy drive, you can simply copy everything from the original disk onto the larger capacity disk, execute SKY, and you are ready to go. After completing the procedures outlined above SILICON SKY is ready to run using default parameters (observing site, etc.). SILICON SKY can be customized for your locality by running the initialization program SETUP. Simply type "SETUP" and hit return. You will be asked whether you have an EGA or CGA graphics card, the name of your default observing site (up to 30 letters), the latitude of your default observing site, the time zone of the default observing site, and whether or not you want to hear a "BEEP" after the display is complete. The beep lets you know that all calculations have been completed. Try it first with the beep. If you find it annoying simply re-run "SETUP" and turn it off. The disk is released with the following defaults: Graphics Card: EGA Default Observing Site: SOUTHERN CALIFORNIA Default Latitude: 34 degrees Time Zone: 8 (PST) Beep: Yes FOR FLOPPY USERS: If you have followed the procedure suggested above, SETUP.EXE is on disk number two. Run SETUP from this disk and it will generate a file named "SISKY87.CLR". Copy this file onto the main program disk. NOTE: Version 2.6 will automatically detect whether or not you have a math coprocessor chip and will take advantage of it if such a chip is present. If a coprocessor is not present the program will run at standard speed. III. Running SILICON SKY To run SILICON SKY simply type "GO" and hit the return. You will see a screen with the SILICON SKY logo and the words "HIT ANY KEY TO CONTINUE"; after following these instructions, the words "STAR DATA LOADING" will appear. This will take from 15 seconds to 30 seconds, depending on whether you are loading from a hard disk or a floppy (floppies take longer). Note: the program reads information from the disk from time to time during execution; therefore, the disk must remain in the drive (or be on a hard disk) while the program is running. MODE SELECTION After the star data has been loaded you will be offered two options: 1. SKY FOR A SPECIFIC DATE 2. PERIODIC UPDATES AT SPECIFIED TIME INTERVALS If you select the first option, one screen will be displayed for the particular date and time you specify. To see another date and time you will have to enter new data. The PERIODIC mode, on the other hand, will display a sequence of screens at an interval you select, beginning with a specified date and time. If you are running the program for the first time, I would suggest starting with option 1. LATITUDE SELECTION The next option is latitude. Two options are available here, the default location selected during initialization or some other latitude. Any other latitude on Earth will work from -90 to +90. If a latitude other than the default has been selected, you will need to hit the enter key after typing in the numbers. DIRECTION OF OBSERVATION The next screen prompts for direction of observation - north, south, east, or west. After one direction has been selected, you will be prompted for date and time data. If a latitude other than the default has been selected the program will prompt you for a time zone from -12 to +12 (Greenwich is 0). TIME FUNCTIONS Finally, the program asks for observing time - year, month, day and hour. Remember to input the month as a number and the hour as a number from 0 to 24. If you are at any latitude other than the default you will be asked for the time zone. PROGRAM EXECUTION The sky will now be plotted on the screen. When the plotting is finished there will be a line at the bottom representing the horizon and curved lines at the top representing the top of the celestial sphere. The display is roughly the field of vision the average person would have looking at the horizon. How long this takes will depend on your system. A "plain vanilla" IBM PC without a math coprocessor will take about 20 seconds to paint the stars on the screen for most horizons. It will take an additional minute or so for the program to examine all of the stars in the data file. Thus, after the program begins to run it will be about one minute and 20 seconds before it is ready to accept new instructions. If you have a math coprocessor or an AT the execution time reduces to a mere seven seconds! SCREEN MENU After the stars have been plotted, a menu will appear at the bottom of the screen. Any option on the menu can be accessed simply by pressing the appropriate number. For example, first option simply removes the menu. Thus, pressing "1" will result in an unadorned display of the sky. ----THE MENU CAN ALWAYS BE RE-ACCESSED BY PRESSING---- ---- THE "ESC" KEY ---- The options and their functions are as follows: 1. REMOVE MENU: Shows sky without menu. 2. OPTIONS: Input new data (latitude, date, viewpoint. 3. SOLAR DATA: Displays coordinates of sun, moon and planets along with date and time data. 4. CONSTELLATIONS: Displays constellations visible in the CENTRAL AREA of the screen. The selection of a particular constellation will plot its boundaries on the display, along with its name. The name can be toggled off with the F1 function key. 5. PLANETS: Identifies solar system objects. The sun and moon are labeled. Planets are identified by a circle drawn around them. 6. SCROLL: This feature allows you to scroll around the celestial sphere. Pressing the appropriate arrow allows you to scroll 360 degrees around the horizon or up from the horizon to overhead. 7. SOLAR SYSTEM: This gives a menu for selecting graphic representations of the moon and bright planets. These are described in more detail in section IV. 9. RETURN TO DOS: Terminates the program. IV. Solar System Display (Selection 7) 1. MOON: The MOON selection will display the moon in proper phase with the major mares and craters marked. For this display NORTH IS AT THE TOP, SOUTH AT THE BOTTOM, EAST TO THE RIGHT AND WEST TO THE LEFT. In other words, in the same orientation that it appears to the eye in most northern latitudes. The data panel below the graphic shows RISE and SET times (in local standard time), the PHASE (% of the surface illuminated) and the position angle of the bright LIMB in degrees. This position angle is defined as the counter clockwise angle between the terminator (line between bright and dark) and the east-west line bisecting the moon. NOTE: The algorithum used to calculate the rise and set times for the moon gives only approximate values. The times are usually correct to within 20 minutes or so, but can be off as much as an hour. 2. MERCURY AND VENUS: Selecting 2 or 3 from the Solar System menu will give, respectively, a graphic of either Mercury or Venus, showing the phase of the planet. Here, as in all planet graphics, SOUTH IS AT THE TOP, NORTH AT THE BOTTOM, WEST AT THE RIGHT AND EAST AT THE LEFT. This is the view through an inverting telescope in northern latitudes. The data panel below shows RISE and SET times, the DISTANCE of the planet from Earth in astronomical units (AUs, where 1 AU = 93,000,000 miles), the apparent SIZE of the planet in seconds of arc, the PHASE (% illuminated) of the planet, and its MAGNITUDE. These data are given in all planetary data panels. For Mercury and Venus the final two items in the data panel are the planet's right ascension (RA) and declination (DEC). For CGA systems, only RISE, SET, DISTANCE and SIZE are displayed. 3. MARS: The Mars graphic shows markings on Mars as would be seen through a telescope at the time and date selected. Pressing function key F1 will display the latitude and longitude grid. The latitude lines are spaced 15 degrees apart, while the latitude lines are separated by 20 degrees. Any point on the visible face can be specified by latitude and longitude by noting the MERIDIAN (longitude line at the center of the disk, specified in the EGA data panel) and adding 15 degrees going right or subtracting 15 degrees per line going left. 4. JUPITER: The highlight of Jupiter is its satellite system. The field of view of the initial the window display may not be wide enough to show all of the satellites, so four different magnifications can be accessed by successive pressings of function F1. For EGA systems, the satellites are color coded and can be identified by pressing function key F2. 5. SATURN: The graphic here shows the orientation of Saturn's rings (South at the top, as with all of the planetary displays). From Earth the rings are seen at varying angles of openness which depend on the location of the planet in its orbit. The rings appear edge on (and, hence, invisible in small telescopes) with a two cycle periodicity (i.e., there will be alternate 15.75 or 13.75 years intervals between edge on appearances). For example, the rings displayed maximum northern exposure in 1987, while they were edge on in 1966 and 1980 and will be again in 1996. V. Updates This program is being distributed as shareware, and it is requested that you register your copy by sending $10.00 to the address below. Payment of the registration fee will entitle you to the next upgrade. I am planning to add the following functions at some future date: -- Coordinates -- Deep Sky Objects -- Milky Way Boundaries -- A more detailed manual Please send registration fee to : Larry Adkins 17652 Wellington Ave. Tustin, CA 92680 ACKNOWLEDGEMENTS The stellar database for Silicon Sky derives ultimately from the Yale Bright Star Catalog; the stars selected are basically the same as those given in Richard Berry's Stars.Bas program (Astronomy magazine, August, 1985). The calculations for planetary positions, phases, rise and set times, and for the satellites of Jupiter are based on formulae given in a 1979 paper "Low-Precision Formulae for Planetary Positions" by Van Flandern and Pulkkinen, "Practical Astronomy with Your Calculator" by Peter Duffett- Smith, and "Astronomical Formulae for Calculators" by Jean Meeus. The constellation boundary data was digitized from the "Sky Atlas 2000" by Will Tirion.