Celestial coordinate system
spherical coordinate systems / From Wikipedia, the free encyclopedia
A celestial coordinate system is a coordinate system that helps astronomers specify the location of objects in the sky. These objects may be stars, planets or even satellites. There are several such coordinate systems listed below. All of them are spherical.
The fundamental plane divides the celestial sphere into two equal hemispheres and defines the baseline for the latitudinal coordinates, similar to the equator in the geographic coordinate system. The poles are located at ±90° from the fundamental plane. The primary direction is the starting point of the longitudinal coordinates.