Ascension

The vertical rising of a planet above the Ecliptic, equator or horizon. Right Ascension, the circle of declination reckoned toward the east from 0° Aries, measured in the plane of the Equator. Oblique Ascension, measured on the Prime Vertical. The Midheaven is directed by Right Ascension; the Ascendant by Oblique Ascension. 

DeVore, Nicholas. Encyclopedia of Astrology. New York: Philosophical Library, 1947.