
 A S T R O N O M Y
 -----------------

the planetarium on TI-82,  positions of the Sun, the Moon and planets 
for any date.
The program is freeware, but it isn't allowed to use it for astrological
purposes.


The program needs less than 8Kb of memory altogether. It uses the variables 
A..Z, L3, L4, L5. All the data required for calculations are stored in 
the program itself.



Installation:
-------------

1. Load  the file ASTRONOM.82g into your calculator.

2. Set your observing place.
(It isn't necessary to set, if you let the original Central European setting,
the program will work with a bit lesser accuracy everywhere around 
the 50 degrees of north latitude.)

In the program O0INPUT find the lines:
50'00' /->/ O        (latitude)
15'00' /->/ N        (longitude)
C-1 /->/ C           (correction of used time in HH.MM to the universal time)
This is the setting for the Middle Europe, 50 degrees of north latitude,
15 degrees of east longitude, 
the correction of the zone time to the universal time is -1 hour.
Correct these lines according your geographical location and  the zone time.
For New York it is for example
        40'45' /->/ O
        -74'00' /->/ N
        C+5 /->/ C

Put the correction for the Universal Time in the first line of the program 
O0TIME.
Now there is for Central European Time
	-1 /->/ H
For New York there will be
        5 /->/ H



Usage:
------

Run the O00SKY, enter Year.MonthDay and then Hours.Minutes. The appearance 
of the sky in given time will be drawn. The Sun, the Moon and planets are 
symbolised by signs described in Pic6 (This picture will be displayed by 
the program O0HELP). The curve represents the horizon. South is in the 
middle, North at the edge of the screen. Each object marked by its sign 
corresponds to the point under the straight line. These points help 
distinguish signs of planets in case they are near each other.
There is marked 50 bright stars. You can easily recognise these  
constellations: Cyg, Uma, Leo, Ori, Cas, And, Peg. The following stars are 
drawn by a greater point: Vega, Deneb, Atair, Arcturus, Sirius and Capela.
You can use the function ZoomIn (or Zbox) for zooming of a chosen area. After
running the Zoom the horizon will be initially drawn. For redrawing 
of the objects it is necessary to run again O00SKY and instead of the date 
give YYYY.MMDD=0. The positions of planets will not be calculated again, 
they only will be redrawn. (On the bottom of the screen will be a note W=0! 
reminding that no calculations were done.)
If you want to change only hours and not the date you can enter only 
YYYY.MMDD=1 and then the time. By that the last zoom will remain and 
no calculations will be done again, the positions of planets will be only 
shifted according to the time. 
(If the time difference is greater the accuracy of drawn positions will be 
lesser.)
You can find the coordinates of the figured objects in L4 and L5. There is
right ascension  in hours in L4 and declination in degrees in L5. 
On the position 1 there is The Sun, 2 - The Moon, 3 - Mercury, 4 - Venus, 
5 - Mars, 6 - Jupiter, 7 - Saturn, (8 - another object) and from 11 
there are stars.

Another objects:

Elements of a next planet, an asteroid or a comet can be entered 
by the program O0XINCMT. (If you enter the element a=0 you can enter 
the distance in the perihelia q.) The elements will be saved in L3. After 
redrawing of the sky by the program O00SKY run the program OXYCMT which 
will calculate and draw the position of the given object.



Accuracy:
---------

The position of stars and the Moon is given with accuracy about 1 degree. 
The stars are here only for rough orientation and better calculation of 
the position of the Moon would be too complicated (more accurate formulae 
and topocentric corrections).
The accuracy of the position of the Sun and planets comes from the solution 
of the problem of two bodies without calculating mutual gravitational forces 
among the planets (about one minute of arc).



The list of programs:
---------------------

O00SKY   The main program
O0HELP   Only redraws Pic6
O0INPUT  Starting setup and input of date and time
O0TIME   Output of date and time
O0TRANH  Transformation into horizontal coordinates (Usage is not written yet)
O0XINCMT Input of elements of another object
O1SUN    Position of the Sun, it must always run before the calculations 
         of positions of the other bodies.
O2STARS  Drawing of positions of stars
OXJUPI   ...
OXMARS   ...
OXMERK   ...     Calculations and drawing of particular planets
OXSATR   ...
OXVENS   ...
OXXMOON  The Moon
OXYCMT   Another object entered by program O0XINCMT
OZDRAW   subroutine
OZKEPLER The main subroutine, it solves (in its first line) the Kepler equation
         and transforms coordinates
OZSKY    subroutine
OZTRAN   subroutine
UMJDIN   The transformation of the modified Julian date into the date
UMJDOUT  The transformation of the date into the modified Julian date
Pic6     help




Advanced usage:
---------------

If you switch on Y3 and Y4 and redraw the sky, the equator and the ecliptic 
will appear.
Programs O1SUN, OXJUPI, OXMARS ... you can also use separately or in your 
own programs. Before you run them you should run O0INPUT to  make start 
setting. The O1SUN must run first (although you aren't interested in the Sun's
position) to transform the coordinates properly.  If you enter W=0 
the calculations will not be done and the previous values will be drawn. 
If you enter T=-1 the equatorial coordinates will be drawn directly. 
There is the modified Julian date in the variable J and it is possible 
to change it. 




Used formulae:
--------------

I used for calculations the adapted formulae from following books:
1. J.Meeus "Astronomical formulae for calculators." Monografieen over 
  astronomie en Astrofyzica, 4, Volkssterrenwatch Urania (Hove) 
  en Vereniging voor Sterrenkunde (Brussel) 1979  
2. (for the Moon) 
  "The Astronomical Almanac for the year 1985." Nautical Almanac Office, 
  Washington, London 1984.




------------------
by Jirka Bubenicek
   bubenic@fnkv.cz
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