Celestial Sphere. If one pictures the sphere we call the Earth, enlarged to embrace the visible heavens, the resulting
concept can be called the celestial sphere. If it is a true sphere, any circle drawn around it can be termed a
circumference. To locate any particular circle as a circumference, implies the selection of some point of reference.
The Horizontal System. If your particular location on the Earth is selected as your point of reference, the point directly
overhead is the zenith. The opposite point, below the Earth, is the Nadir. At right angles to these is a plane which is
called the Horizon: the extension to the Celestial circle of the line which, from the point you occupy, intersects earth and
sky. These established, you have a Vertical circle running from the Zenith, through a middle point between East and
West, to the Nadir; and similar circles running through each degree all around the horizon. The distance of each of these
circles from your circle is measured by the arc at which the circles intersect at the Zenith - termed Azimuth. Parallel to
the Horizon are Parallels of altitude. These are measured by the arc separating the radius of your horizon from a line
drawn from the same center to a given parallel of altitude.
The trouble with this system is that a location based upon your position fails to describe the same location as viewed
from any other point on the Earth's surface.
The Equator System. This takes as a point of reference the diurnal rotation of the Earth around its axis. Extending the
North and South poles, you have the North and South Celestial poles. Extending the Equator, you have the Celestial
Equator. The Equator is intercepted by Hour Circles, whereby location is indicated in hours and minutes of Right
Ascension, measured Eastward from the Zero Circle which passes through Greenwich. Parallel to the Equator are
Parallels of Declination, indicated by their angular distance plus, if North of the Equator; and minus if South.
With your celestial sphere marked off on this system, it can be seen that the Sun does not travel around this Celestial
equator; but instead, its orbit is inclined to that of the Equator some 23.5 degrees. The points at which the Sun's apparent
orbit intersects the Equator are the Equinoxes, and the points of greatest separation are the Solstices. (These names have
to do with an entirely different but coincidental factor. v. Precession.)
The Ecliptic System. The path of the Sun, called the Ecliptic, is based on the annual revolution of the Earth around the
Sun. Taking this apparent path of the Sun as a circumference, you have at right angles thereto the North and South poles
of the Ecliptic: connected by vertical circles of Longitude measured in degrees Eastward from the Vernal Equinox.
Circles parallel to the Ecliptic are measured in degrees of Latitude North or South.
Stretching for some 8 degrees on either side of the Ecliptic is a belt in which lie the orbits of all the solar system bodies,
each inclined in various degrees to the Earth's orbit. Since Hipparchus (q.v.), the greatest of the ancient astronomers, this
belt has been divided into twelve 30° arcs, or signs, measured from the Vernal Equinox; the signs named from the
constellations which once coin- cided with these arcs, but which because of the Precession of the Equinoxial point now
no longer coincide. The statement that this disproves astrology is sheer ignorance, for no modern astrologer ascribes the
sign influences to their background of stars, but to conditions of momentum and gravitation within the earth by virtue of
its annual revolution around the Sun. (v. Zodiac; Precession; Galactic Center.) Many of these terms are loosely used by
some astrologers, largely because they lack complete astronomical understanding of the factors on which their map of
the heavens for a given moment is erected. (v. Map of the Heavens.)
Vertical Sphere. The circle of observation in which one stands when facing South (probably so termed because it is the
observer's horizon raised vertically and projected upon the heavens), is the circle that is presumably subdivided into
twelve equal 2-hour segments as it passes over the horizon, which divisions are termed the Houses of a Nativity. On the
Equator these Houses are equal in both time and arc, but they become increasingly unequal in arc as one passes N. or S.
from the Equator. This results from the declination of the Poles, and the consequent inclination of the Ecliptic to the