Celestia Forums

Thanx for document. I found there another one definition: Observer table coordinates, such as RA and DEC, may be with respect to two possible coordinate systems: Earth mean equator and equinox of reference epoch (astrometric coordinates): Reference epoch: J2000.0 or B1950.0 xy-plane: plane of the Ea...

What is the difference between horizons's astrometric and apparent ephemerides?