Astronomy for Astrologers
360° orbit of the Earth around the Sun describes a
plane that passes through the center of the Earth and
through the Sun. By definition, our Earth moves only
within this thin plane, in its endless orbit around the Sun.
In the diagram, the Earth revolves in a counter-
clockwise direction (as seen from looking down from the
north pole of the ecliptic).
Tropical Zodiac
The Ecliptic Plane
Let's examine what the zodiac or ecliptic coordinate
system is and how we use it in our work. All reference
coordinate systems (such as the ecliptic) must have a
center. For what we are talking of here, that center will
be either the Earth or the Sun. We use the Earth as a
center for traditional geocentric (Earth-centered)
astrology and the Sun as the center for heliocentric
(Sun-centered) astrology. As far as the zodiac is