
plan404 ephemerides

The tables of coefficients were derived by a least squares fit of
periodic terms to JPL's DE404 ephemerids.  The periodic
frequencies used were determined by spectral analysis and
comparison with VSOP87 and other analytical planetary theories. 
The least squares fit to DE404 covers the interval from -3000 to
+3000 for the outer planets, and -1350 to +3000 for the inner
planets.

The files mer404.c, ven404.c, ..., plu404.c contain numerical
tables for computing the J2000 heliocentric ecliptic longitude,
latitude, and distance of the indicated planet.  Each file
includes a table of statistics from a comparison with DE404.
Maximum deviations from DE404 are shown, in arc seconds, over each
interval of 500 Julian years. The figure tabulated for deviation
in radial distance is scaled relative to the mean distance; to
convert to astronomical units, multiply by 4.848e-6 times the
mean distance in au.

Program example.c shows how to use the tables in conjunction with
the subroutine gplan.c.  The program takes a Julian date as a
command line argument and prints an ephemeris of the Moon and
planets for that date.  The codes have been tested with Microsoft
C version 6 and on Unix systems.

A program for Lunar positions was posted previously.  It was
adjusted to DE404 using the precession formulas by Simon et al
(1994).  The version included here uses the precession of
Williams (1994) which should be more compatible with the JPL
ephemeris.

Steve Moshier
moshier@world.std.com
December, 1995
