descension
De*scen"sion, n. Etym: [OF. descension, L. descensio. See Descent.] Defn: The act of going downward; descent; falling or sinking; declension; degradation. Oblique descension (Astron.), the degree or arc of the equator which descends, with a celestial object, below the horizon of an oblique sphere. -- Right descension, the degree or arc of the equator which descends below the horizon of a right sphere at the same time with the object. [Obs.]