The Astrology of Space - Matrix Software

The Astrology of Space
Horizon Coordinates
In the Horizon system a plane through the observing
point parallel to the horizon is the plane of reference.
The poles are the Zenith (point overhead) and the
Nadir (point underfoot). The vertical circle through a
celestial object (such as a star) and the zenith is the
Object Circle. The coordinates are given (for the
object) by Azimuth, which is the horizontal angle (A in
the diagram) measured from an arbitrary reference
direction – East in our case – counterclockwise to the
object circle) and the Altitude (a), which is the
elevation angle measured upward from the horizon to
the object). The great circle through the north and
south points and the zenith is the Meridian, and the
great circle through the east and west points and the
zenith is the Prime Vertical. Circles of parallel altitude
to the horizon that are not great circles are called
Almucantars.
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