The celestial sphere, eliptic & presession

This is a Celestial sphere, an imaginary sphere of a large radius encircling the Earth and rotating upon the same axis, concentric with the Earth. All objects in the sky can be thought to be projected onto the sphere. The celestial equators and celestial poles are projected right above the earths equator and poles.


This is a diagram of an ecliptic, the supposed path that the Sun travels throughout the year, tracing an imaginary line on the celestial sphere, which is intersected by the ecliptic of the earth (The Geometric plane) in which the earth orbits the Sun. The name refers to the fact that when the full or new moon meets the Sun on its path.

This is a model of precession, a change in the orientation of the rotation axis of a spinning object. It can be defined as a change of direction from the rotation axis.