a celestial sphere is an imaginary sphere of gigantic radius with the earth located at its center. The poles of the celestial sphere are aligned with the poles of the Earth. The celestial equator lies along the celestial sphere in the same plane that includes the Earth's equator. We can locate any object in the celestial sphere by getting to coordinates called the right ascension (longitude) and the declination (lattitude) so known as the celestial coordinates.

ecliptic, preccsion