C library for the Swiss Ephemeris
libswe0 allows programs to access the Swiss Ephemeris.
The SWISS EPHEMERIS is the high precision ephemeris developed
by Astrodienst, largely based upon the DE406 ephemeris from NASA's JPL.
The Swiss Ephemeris is based upon the latest planetary and lunar
ephemeris, DE405/406, developed by NASA's Jet Propulsion
Laboratory. The original integration, DE405, covered the years 3000 BC
to 3000 AD and required 550 Mb of disk space. DE406 is a compressed
version of DE405 which requires 200 MB while maintaining a precision
of better than 1 m for the moon and 25 m for the planets. These data
have been further compressed with sophisticated compression techniques
developed by Astrodienst. The ephemeris now requires for the complete
6000 years only 5 Mb for all planets except the Moon, and 13 Mb for
the Moon. This compressed ephemeris reproduces the JPL data with 0.001
arcseconds precision. Astrodiest's have extended the timespan of the
JPL ephemeris by numerical integration, so that Swiss Ephemeris covers
the years 5400 BC to 5400 AD, a total of 10'800 years. For this extended
timespan the ephemeris requires 32 Mbytes of ephemeris files.
All transformation steps from the inertial timeframe of the JPL DE406
integration to the reference frame for astrological coordinates (true
equinox of date), all corrections like relativistic aberration,
deflection of light in the gravity field of the Sun etc. have been
performed with utmost care and precision so that the target precision
of 0.001 arcsec is maintained through all transformation steps. Never
before has such a high precision ephemeris been available to
astrologers.
Swiss Ephemeris contains three ephemerides. The user can choose
whether he/she wants to use the original JPL DE406 data (if available
at his/her site), the compressed Swiss Ephemeris data (the default) or
a built in semianalytic theory by Steve Moshier. The Swiss Ephemeris
package switches automatically to the available best precision
ephemeris dependent on which installed ephemeris files it finds. Even
without any stored ephemeris files, using the Moshier model, planetary
positions with better than 0.1 seconds of arc precision are available
(3 arcsec for the Moon).
In addition to the astronomical planets as contained in the JPL
integration, Astrodienst's have included all other bodies and
hypothetical factors which are of interest to the astrologer.
Astrodienst have used Astrodienst's own numerical integration program
to provide ephemerides for ALL known asteroids. There are over 55'000
of them and nobody will be able to use them all. Astrodienst distribute
these extended asteroid files via Astrodienst's download area; there
are also CDROMs available with large sets of asteroid files. Asteroid
reaserachers may be interested in a December 1998 article in the
Economist magazine about the naming of asteroids.
Speed: The Swiss Ephemeris is precise and fast. On Astrodienst's Linux
test machine, a 1000 MHz Pentium III, Astrodienst compute 10'000 complete
sets of planetary positions, i.e. 10'000 x 11 planets, in 9 seconds. This
is 0.9 milliseconds for the complete set of exact planetary positions
(consecutive 1 day steps).
