ron@vicorp.com (Ron Peterson) (01/17/91)
Archive-name: astro/planets/ephem/1991-01-15
Archive-directory: mandarin.mit.edu:/astro/ephem/ [18.82.0.21]
Original-posting-by: ron@vicorp.com (Ron Peterson)
Original-subject: C Code for planet locations (long)
Reposted-by: emv@ox.com (Edward Vielmetti)
I've received a lot of requests to share any info I get on plotting the
position of the planets so here's a summary of the responses I got.
Given the level of interest perhaps the ephem source code should be
posted also. (I've got the code but not the manual text.)
From: <uunet!cc.flinders.edu.au!A.C.Beresford> <phacb@cc.flinders.edu.au>
Ron, you will find formulae in
1. peter duffet-Smith's astronomy & your personal computer
2. Jean Meeus's Astronomical formulae for calculators
3. Simon & bretagne planetary positions -9000 to +4000
Code from 2 is available as the ephem program on
group comp.source.misc, and i think for anon FTP
from mandarin.mit.edu. IBM PC versions of ephem are
also avalable on ibm.pc.binaries and on simtel20
and its copies.
From: uunet!minyos.xx.rmit.OZ.AU!s882080 (Paul Taylor [Falcon])
The program Ephem by Elwood Downey (downey@dimed.com) has a text "graphics"
display of the planets positions. These can be viewed as a sky-map, or a
orbit position display on the solar system. If you aren't satisfied with
his program (which is excellent in its own right), you can always use the
routines it contains. Contact Elwood directly for information on where
to get the source code.
From: Steve Penton <uunet!ssl.Berkeley.EDU!spenton>
Here is a manpage that I found, I don't know if its what we use.
starchart(LOCAL) UNKNOWN SECTION OF THE MANUAL starchart(LOCAL)
NAME
planet, epoch
- print phase of the Moon and planetary information, precess data
in .star file format.
SYNOPSIS
planet [juliandate]
or
planet [-z timezone -m month -d day -y year -t hh.mm ]
epoch [ inputepoch ] [ outputepoch ]
DESCRIPTION
These programs generate and maintain star chart data in the for-
mat used by the starchart software tools.
Planetary information is generated by the program planet, which
calculates locations a given Julian date, or for the current time
(given no arguments). In common use, an alternate syntax is pro-
vided to simplify the calculation of the Julian date, in which
integers for month, day, (mandatory), and year are given. Time is
specified in the form hh.mm or hh on a 24-hour clock and defaults
to 0.00 (midnight). The -z flag (same format as -t) gives the
number of hours the observer is west of GMT (see below).
A summary is then printed on the standard output giving the right
ascension, declination and distance (in AU's) for the Sun and all
planets except Pluto. This data is additionally placed in the
file planet.star for subsequent use by charting software.
The program epoch converts right-ascension and declination data
within yale.star style datasets from epoch 1975.0 into the epoch
2000.0. Either the first or both epoch dates may be overridden
with command line parameters (floating point values). The data is
read and written from the standard input and output. Because only
the coordinate data is updated within each line item, the program
may be used on either versions of the reduced Yale data.
BUGS
Daylight savings time may have to be reckoned for in planet, as
the default -z value during periods of daylight time may or may
not be adjusted relative to GMT. The required code changes would
make planet installation dependent.
AUTHORS
planet - F.T. Mendenhall <ihnp4!inuxe!fred> Jim Cobb
epoch - Alan Paeth, University of Waterloo <AWPaeth@watCGL>
-Craig Counterman <ccount@athena.mit.edu>
yale.star - Robert Tidd <inp@VIOLET.BERKELEY.EDU>
messier.star - Bob Tidd and Alan Paeth
SOURCES
planet - Astronomical Formulae for Calculators by Jean Meesus
Solbourne Computer, Inc. 6/2/87 1
starchart(LOCAL) UNKNOWN SECTION OF THE MANUAL starchart(LOCAL)
epoch - Celestial BASIC by Eric Burgess (SYBEX 1982) Astro-
nomical Almanac
Solbourne Computer, Inc. 6/2/87 2
From: uunet!RELAY.CS.NET!randall%thor.sandiego.ncr.com
Elwood Downey posted to the net an ephemeris program in c that
displays the sun, all planets, some asteroid and comets, but all
from a geocentric, not heliocentric position. The program has
several display modes.
From: uunet!EPS.GVL.Unisys.Com!joef (Joe Fedock)
EMail downey@dimed.com and ask for ephem. Has C code and probably does all
you need to do. The gentleman's name is Elwood Downey. I've been using ephem
for about a year now. I also use it to generate the comet ephemerides that
I regularly post to sci.astro. I don't think you'll be disappointed. The only
other routine that I know of that is more accurate is ICE from the Floppy
Almanac office of the USNO in Washington, DC. That is written for a PC and is
highly accurate, but not nearly as versitile or nice to use as Elwood's
program.