ASTRO An Astronomy Program By Don Thayer January 3,1987 Files description: ASTRO.COM ...... Standard EGA Astronomy Program ASTRO87.COM ..... EGA with 8087 Coprocessor Version ASTRO.TXT ....... This Document Please note: Both these programs require an EGA card to run. ASTRO87.COM also requires a 8087 math coprocessor. Both programs check for the presence of an EGA card, however, ASTRO87.COM will hang a computer that does not have the 8087. The algorithms for calculating data for "Orbital Data of Planets" and "Rise and Set Times" were translated to Turbo Pascal from a basic language book titled "Celestial Basic" by Eric Burgess published by Sybex. From the Selection Menu, you can choose four different astronomy routines. Whenever you quit from one of these routines, you will be returned to this menu. To exit from the program altogether, press the "Q" key from the Selection Menu. ****** ASTRONOMY ROUTINES ****** ORBITAL DATA OF PLANETS: This routine calculates the Heliocentric Longitude (in degrees), Distance from the Sun (in AU), Right Ascension (in hours), Declination (in degrees) and the Distance From the Earth (in AU). Once the data has been displayed, the following line will be displayed at the bottom of the screen: G = Graph P = Print N = New Date Q = Quit Press the "G" key for a graphic representation of the solar system. Press the "P" key for the data to be printed on the printer. Pressing the "N" key will prompt you for a new date and pressing the "Q" key will return you to the Selection Menu. If you choose to print the data on a printer, the program will ask if you want to advance the printer. Pressing the "Y" key will advance the printer to the top of the next sheet. This option was added because you can print up to any two sets of data on one sheet if you wish. The graphics of the solar system shows relation ship between the planets and although the distances between the orbits are proportional, the orbits themselves are circular instead of the true elliptical ones. The orbit of pluto is not shown and for certain dates (such as Jan. 1, 1900) the planet is off the screen. ******* RISE AND SET TIMES: This routine will calculate the approximate rise and set times for all the planets plus the Sun and Moon. Also shown is the transit time, R.A., declination, distance from the Earth and the angular distance from the Sun. After the data is displayed you may print the data on the printer, select a new date or quit to the Selection Menu. ******* PHASES OF THE MOON: This routine requires only the Year and Month. Once this is entered, the program calculates the date of the first full moon prior to the date entered and then will display the next three sets of dates for the four phases of the Moon. ******* SOLAR SYSTEM SIMULATOR: This option will produce a graphic working model of the solar system. In addition to the year, month and day, this routine also requires the interval in days, the innermost planet and the Outer planet. The interval in days affects the speed at which the planets appear to move. Since Mercury travels around the Sun in approximately 88 days, it will move fairly rapidly with a one day interval. Pluto on the other hand will require an interval of several hundred days. The interval you enter must be an integer greater than zero. After the interval in days is entered, the program will prompt you for the "Innermost Planet Number" and then the "Outer Planet Number". Select the planet number from the table shown at the bottom of the screen. Also the outer planet number must equal to or greater than the innermost planet number. If you wish, you can display all 9 planets on the screen at the same time, however, the inner 4 planets will only appear as a blob in the center of the screen. Once the simulator is running, there are several options that can be chosen. These are displayed in the lower left corner or the screen. Pressing the "I" key will prompt you for a new interval. If you wish, you can enter a negative number and watch the planets move backwards. This is helpful if you want to see a specific date again. While the simulator is running, certain information is being updated on the screen. The "S" key toggles this updating on and off. The writing of this data on the screen takes time and slows down the graphics. Although the performance on the non-8087 version is small, the 8087 version can be dramatically improved by turning off the status. The "C" key will clear the screen and the tracing of the planets paths will start where the old screen left off. This is particularly useful when some of the inner planets paths have made a complete revolution. It is also useful when you change the direction of movement using the "I" key. Pressing the "P" key will temporarily halt the simulator. Press any other key to start it again. If you press any of the other option keys, they will take effect at this time. To quit the simulator and return to the Selection Menu press the "Q" key. ******* SAMPLE DEMONSTRATION: Start the program and select option for the simulator. Enter the date of May 1, 1988. Enter an interval of one (1) and select Mercury as the innermost planet (1) and Mars (4) as the outer planet. Around June 13,1988 you should see the opposition of Mercury, Venus and Earth. A little later in the same year, around September 26 you should see the opposition of Earth and Mars. You may want to compare the the Heliocentric Longitude's of these planets for these dates using option from the Selection Menu. ******* ACCURACY: This program is by no means exact. To the best of my knowledge it is fairly accurate, however, there are a number of astronomical corrections not allowed for such as precession. Also much of the original data was limited to only a few significant figures. Admittedly this makes poor use of the 8087 with its 16 digit accuracy. From an astronomer's point of view, my knowledge of astronomy is nil and of the related math, it is even less. There are several very good astronomy program available for the PC, however, none of them that I have found combine the planetary data and graphics the way this one does. If you have any comments, suggestions or information on how I can increase the accuracy of this program, please write to me at the following address: Don Thayer 1675 Hays St. #207 San Leandro, Ca 94577 The programs ASTRO.COM and ASTRO87.COM along with this document file may be distributed freely among users and user groups in their original and unmodified form. No profit either monetary or otherwise shall be gained from the sale of these programs.