
"P" is a program which displays all sorts of astronomical data about
the Sun, Moon, and planets.  The algorithms were taken from Duffet-Smith's
book, "Practical Astronomy with your Calculator".

All of the accuracy limitations described in the book apply, of course,
to this program.  (Positions +- ~1 deg.; rise/set times +- ~5 min.)

The program displays the following data in the upper part of the screen:

	- RA (in hours and minutes) of Sun, Moon, and planets
	- DEC (in degrees) of the same
	- Azimuth and elevation (in degrees) of same
	- Rise and set times of same
	- Distance (in astronomical units) of same
	- Light travel time (in hours and minutes) of same
	- Apparent diameter (in arc seconds) of same
	- Phase of same
	- Apparent magnitude of same

A matrix of angular separation (in degrees) of the planets is displayed
in the lower half of the screen.

A line near the bottom of the screen displays the date and the time.
The time is presented in Local, Greenwich Mean, Greenwich Siderial,
and Local Siderial formats.

The bottom line is used for input when the program is run in
interactive mode.

The Lunar and Solar eclipse calculations are included, the comet
calculations are not.



Here are some examples of running the program:

	$ p

In this mode, "p" will prompt you for the time (HH:MM:SS) and
date (MM/DD/YYYY).  The program will display the values and exit.
Use a negative YYYY for years B. C.



	$ p -n

In this mode, "p" uses the current time and date for the calculations.



	$ p -n -l

The program will use the current time and date for the first
calculation and then repeat the calculations using a default delta
of one day.  The program is running in interactive mode, so you
can vary the delta as you watch.  The interactive commands are:

	>>> r<cr>		for reverse (or negate) the delta value

	>>> <number><X><cr>	where <number> is a floating point
				number, <X> is one of
					NULL	for day (default)
					s	for second
					m	for minute
					h	for hour
					d	for day
					w	for week
					y	for year

	>>> n<cr>		reset the internal date to "now"

	>>> e<cr>		enter elapsed time mode; this only
				works for reasonable values of delta.

	>>> ne<cr>		leave elapsed time mode

	>>> nl<cr>		leave looping mode

	>>> q<cr>		quit the program




If you want printed output instead of displayed output, add "-p"
to the command line.

The default delta of one day in looping mode can be overridden by
adding the desired delta after the "-l" (with no white space)
on the command line.  The format of the delta is that of the
interactive delta described above.

Necessary local mods:

	There are four #define's, HERELONG, HERELAT, HERELEV, and
	HEREZONE, that must be defined to be your longitude,
	latitude, elevation, and timezone, respectively.  Look in
	p.h for more details.


This program has been run only on AT&T versions of UN*X.

Enjoy.

					Ron Kukuk
