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