Provides general classes for basic ephemeris calculation.
This package contains algorithms designed to calculate position of Sun, planets, the Moon, comets and asteroids, space probes, and artificial satellites.
It is possible to apply different methods for precession, nutation, obliquity, and mean sidereal time, following different conventions that have been modified during the years. The last situation is called IAU_2009 method in this library. In this case, nutation is calculated using IAU2000A theory of nutation (Mathews et al. 2002), and precession is performed by applying Capitaine et al. 2006 method, as it is recommended by the report of the IAU Division I Working Group on Precession and the Ecliptic (Hilton et al. 2006). Support for the precession part of the IAU2000 precession-nutation model is given (iau2000 method), but it has been declared to be inconsistent with equations of motion. The use of the IAU2000 model as it is implemented here gives positions with an accuracy up to the milliarcsecond level, but only for current epoch.
There are several frames to obtain the results of the ephemeris. The old FK4, FK5, and dynamical equinox of J2000 frames are available for consistency with old catalogs. The new ICRF frame is the one recommended by IERS 2003 conventions, and officially adopted by the IAU. They differ by as much as 0.01 arcseconds respect to the dynamical equinox of J2000 epoch.