mean equator and equinox

mean equator and equinox

The reference system determined by ignoring small variations of short period in the motions of the celestial equator; it is affected only by precession. Positions in star catalogs are now usually referred to the mean catalog equator and equinox (see catalog equinox) of a standard epoch. The coordinates of a celestial body on the (Sun-centered) celestial sphere, referred to the mean equator and equinox of a standard epoch, are its mean place. See also true equator and equinox.

Collins Dictionary of Astronomy © Market House Books Ltd, 2006