This section describes the ecliptic and ecliptic plane.
The Ecliptic Plane is defined as the plane that contain the orbit of the Earth around the Sun.
The Ecliptic is defined as the intersection of the Ecliptic Plane and the Celestial Sphere.
The following picture provides a good illustration of the Ecliptic and Ecliptic Plane in
the Celestial Sphere system, http://www.astro.virginia.edu
Notice that we have two base circles on the Celestial Sphere now: Ecliptic and Celestial Equator,
Looking at the Ecliptic and the Celestial Equator on the Celestial Sphere, you will see:
Earth's Inclination is the angle between the Ecliptic plane and the Equator plane, which is almost a constant of 23.5 degree.
Equinoxes, the Vernal Equinox and the Autumnal Equinox, are two intersection points of the Ecliptic and the Celestial Equator.
