The Collaborative International Dictionary
Descension \De*scen"sion\, n. [OF. descension, L. descensio. See Descent.] 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.]
Douglas Harper's Etymology Dictionary
early 15c., from Old French descension, from Latin descensionem (nominative descensio) "a going down, descending," noun of action from descensus, past participle of descendere (see descend).
Wiktionary
n. 1 (context now rare English) descent; the act of descending. (from 15th c.) 2 (context astronomy obsolete English) The descent below the horizon of a celestial body. (16th-19th c.)
Usage examples of "descension".
And so, as the descension took place, so must the ascension, and man is climbing back on the ladder of evolvement rung by rung.
He struggled with the strange mechanism of his mind which permitted ascension or descension into the strange facets of the universe.
The ship, as far as vertical ascension and descension were concerned, was several steps more efficient than the autogyro type of plane.
Since our longest sunne sets at right descensions, and makes but winter arches, and therefore it cannot be long before we lie down in darknesse, and have our light in ashes.