This astronomy stack is designed to ease the calculations associated with rising, setting and positions of the sun and planets. The positions are calculated using low-precision Chebyshev polynomials found in the annual publication "Almanac for Computers" published by the U.S. Naval Observatory. The items are entered in hidden background fields on each card, one field for R.A. and one for declination. These may be made visible and must be updated each calendar year. For some planets the position calculations may take 15 seconds or so and is designated by a sad face. The altitude/azimuth calculations are quicker and are denoted by a smiling face.
The observers latitude, longitude (east=positive), altitude and hours difference from UT are entered on the first card. The DST button is automatically set if Daylight Savings Time is in effect. Universal Time and Sidereal Time are calculated as well as the Julian Date. A Jovian Galilean satellite button is seen on the Jupiter card and this links to my JSAT emulation program (available on GEnie or directly from me).
The time for Algol's next minimum is calculated and displayed on card 1.
Holding down the shiftKey bypasses RA and Dec. calculations.
Holding down the optionKey forces the calculations to be performed.
The button "Update for Today" updates all cards and fields to the present time/date and takes about 1.5 minutes to run. It is very useful at the beginning of a session.
A card is given to assist with astrophotography. The formuale are based on Barry Gordon's book, "The fx System of Astrophotography".
A planetary conjunction card is now included. Enter the threshhold value in degrees and all planetary conjunctions less than the theshhold value will be listed.
The dates of maximum ZHR of selected meteor showers are calculated on a separate card. Olson, Sky & Telescope, 78(2), 195, 1989.
Jupiter Galilean Satellite Timing Predictions are displayed for the current date. The script now asks for the user to select the file. To change the file for a change of years, hold down the command key while moving to the Jupiter card. The filename is stored in the third line of the script. Don't move it from there. The file for the current year is included. Additional information may be obtained from John Westfall, ALPO, Box 16131, San Francisco, CA, 94116, USA
Positional coordinates may be converted from 1950 to 2000 epoch and back. Also, they may be converted to altitude and azimuth for use in observing.
The Moon card has been added/enhanced. Approximate R.A. and Dec. calculations have been incorporated using formulae from the Astronomical Almanac (1990, D22). Moon rise and set times are calculated, but the moon's position is iterated only once to the time of the event and may be in error (+/- 5 minutes). NOTE: This card may also total lunar occultation information. If you have access to total lunar occultation predictions, then entering them in a file in a similar format to the included example file will allow one to see each day's occultations. If you do not have access to these data, then use the "Delete Occultations" button.
Calculations for the longitude of Jupiter's central meridian have been added (Sky & Telescope 78(6), 640, 1989. This enables the transit time of Jupiter's Great Red Spot
to be predicted. The System II longitude of the Red Spot is assumed to be 22┬░ (as of March 1990). A 1┬░ drift in longitude causes the spot to rise 1 2/3 minutes sooner or later. The spot is well placed for viewing for 1 hour before and after the predicted time of crossing.
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