Herong's Notes on Astrology and Horoscope - Version 2.11, by Dr. Herong Yang
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:
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