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 Equator. The planets which
are posited in these signs pass obliquely
through the semi-arc of the Ecliptic to
the Mid-heaven - not the zenith. Therefore
the position which a planet will occupy at
some future moment, to which it is desired
to direct it, must be calculated by Oblique
Ascension.
In
an effort to reconcile the rising or
ascendant moment at which a planet passes
above the horizon, with its oblique
ascension along the Ecliptic to a
mid-heaven point that is on the same
longitudinal circle as the Zenith, but a
considerable distance removed from it,
various attempted compromises have
resulted in several different systems of
House Division (q.v.). The
horizon system appears to yield the
correct House positions of the planets in
a birth map, but the directing (q.v.)
of planets to the positions they will
occupy at some future moment, requires the
application of Oblique Ascension, both to
the planets' places and to the progressed
cusps.
For
a concise classification of the term, note
the appended table:
THE
CELESTIAL SPHERE
Circle
of reference Horizon
Celestial Equator
Ecliptic
Poles
Zenith
N. celestial pole
Midheaven
Nadir
S. celestial pole
Immum Coeli
Secondary
Circles Vertical
circles Hour
Circles
Latitude circles
Parallels of altitude Parallels of
declination Parallels of Latitude
Coordinates
Altitude
Declination
Celes. Latitude
Azimuth
Right Ascension
Celes. Longitude
Zero
Circle
Vertical c. thru S. Hour c.
thru Ver.
Latit. c. thru V.
point
Equinox
Equinox.
Direction
of first Through West Eastward
Eastward
coordinate
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