Sun_Ephemeris


SUN EPHEMERIS GENERATOR V1.5
Program written by Jay Tanner - Jay@NeoProgrammics.com
It was built around revision 6 of the VSOP87 core modules.
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The program is based on an implementation of the full VSOP87 theory
computations of the orbit of Sun in spherical variables.
The original VSOP theory was developed of Pierre Bretagnon et al. of
the Bureau des Longitudes in Paris and was implemented in the FORTRAN
computer language.
Theoretically, the heliocentric coordinates upon which the geocentric
computations are based are accurate to within an arcsecond or better
over the range from 2000 BC to 6000 AD in the case of the inner
planets, Mercury to Mars.
Due to the popularity of Microsoft Visual BASIC and the much faster
speed of modern computers, I thought it was about time to develop a
version of the theory that would be more accessible to the amateur
astronomers with Windows PC computers. The result of that effort is
the development of a series of ephemeris generating programs for the
Sun and the eight major planets from Mercury to Neptune.
The computations of the planetary positions include the interacting
gravitational perturbations of the planets, precession, the long-term
effects of relativity, light-time, aberration and nutation. Then the
coordinates of the planets are reduced from the dynamical coordinates
of the VSOP87 theory to the apparent geocentric coordinates according
the standard J2000 FK5 system of coordinates. Consequently, the
computations compare very favorably with the published ephemerides.
The basic ephemeris computations are:
Apparent Geocentric:
Right Ascension
Declination
Distance to the sun
Semidiameter

The planetary orbits are determined by the computation of three
spherical variables.
These variables are:
   L = Heliocentric longitude
   B = Heliocentric latitude
   R = Radius vector or distance between centers of Earth and Sun

Program Statistics for the Sun ephemeris program:

Total Computational Term Counts For the VSOP87 Orbit of EARTH are: 
Total # L Terms: 1080
Total # B Terms: 348
Total # R Terms: 997
Total All Terms: 2425
The Earth module is used to compute the position of the sun. This is
the simplest case, since the Sun may be considered directly opposite
the Earth. In this case, the position of the Earth is computed and
180 degrees is added to its heliocentric longitude and the sign of
the Earth's heliocentric latitude is reversed. The radius vector
requires no modification.
======================================================================

Original Author: Jay Tanner

Inputs

Data and Time

Returns

High precision ephemeris of geocentric solar coordinates over an 8000 year period.

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Posted: 2002-06-01
By: ArchiveBot
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