from
The Collaborative International Dictionary of English v.0.48
Descension \De*scen"sion\, n. [OF. descension, L. descensio. See
{Descent}.]
The act of going downward; descent; falling or sinking;
declension; degradation.
[1913 Webster]
{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.]
[1913 Webster]