Planets Documentation
---------------------

By Tim Strong

This program calculates the positions of the planets in the sky.

You don't have to know anything about julian days or anything like that
the planet finder invokes them internally. However the functions are
available.

Simply load the directory into your calculator and press CST.
(Incidentally make sure you machine is in DEG mode or your answers
will come out in radians. After pressing CST you will get the following
options:

PLAN		This key runs the planet finder. I have tried to make it as
		user friendly as possible since after a few weeks I'd forget
		how to use it if it weren't.

CONC		This key invokes a menu driven astronomical coordinate
		conversion program. I will describe its use in a few minutes.

DMS->		This key takes two coordinates that are on the stack in
		HH.MMSS or DDD.MMSS format and converts them to decimal.
		Basically it invokes the built in HMS-> twice.

->DMS		This key does the reverse of the above but also tags the output
		so you know its in HH.MMSS form.

JULDAY		This key finds the julian day for any date. Its input is month
		on stack level three day on level two and year on level 1.
		Fractional days can be used to indicate different times
		during the year.

deltaD90	This key finds the number of days since the epoch of 1990.
		This is the epoch the internal coordinates or values for the
		planets orbit elements are set for.

epoch		This variable contains the current epoch in which you want the
		coordinate to be figured.  If your star maps are labled epoch
		2000 you put 2000 in here.

phi		This variable contains your local latitude in decimal form.
		set it for your viewing location.

epsilon		This variable will find the obliquity of the eliptic for
		for the current epoch.

First try PLANETS. A menu across the bottom comes up showing all the
planets and you aare instructed to " ENTER DATE M DD YYY and select planet
Simply do that ( for example if I want to know all about Jupiter tonight
I enter 6 20 1991 and then press JUPIT.  After ten seconds I get the following
display (the greek letters are spelled out)

alpha= 9.0000
delta= 17.4839
rho= 6.0239
tau= .5006         Jupiter
theta= 32.6598
F= .9956
m= -1.8574

alpha is the right ascension it reads as 9hr 00min 00sec. Delta is the
declination which reads as 17deg 48min 39sec. rho is the number of astronomical
seconds.  Theta is the angular diameter of the planet (how large it will
appear in a telescope) in arcminutes. F is the current phase of the planet
in percent lighted. m is the visible  magnitude of the planet.

Now the numbers for right ascension and declination should be accurate to
within a minute or two (mercury could be worse). Also the magnitude is
probably a bit optimistic.

Next press CONCO. If there is less than three items on the stack you will
see a menu of conversions and the words "select conversion:"  put the
coordinates you want to convert on the the stack in decimal notation (use
->DMS if you want to) and then press the appropriate conversion. If there
are three items on the stack the program assumes it hass been callet by
another program. In this case the following arguments should be on the stack:

3: first coordinate
2: second coordinate
1: number of conversion

the number of the conversion is simply the number of the conversion you want
from the menu numbered left to right.

Some facts about the program.

   1)  Please feel free to modify it in any way.

   2)  The program is quite long 4679.5 bytes. I did that to make it
       user friendly and because its my first large program (its not
       particularly efficient).

The following reference should be sighted as I used it heavily in order to
find an algorithm to find the values:

Practical Astronomy with your Calculator--Peter Duffet Smith  3rd. edition
Published by the Cambridge University Press 1988.

This book is excellent if your interested. It even shows how you can use
you calculator to predict and picture a solar eclispe. All the routines
shown are algorithms that you work out by hand and write down intreceeding
results, but they can be programmed with some work (kinda like I did).
