The Collaborative International Dictionary of English v.0.48:
Ascensional \As*cen"sion*al\, a.
Relating to ascension; connected with ascent; ascensive;
tending upward; as, the ascensional power of a balloon.
Ascensional difference (Astron.), the difference between
oblique and right ascension; -- used chiefly as expressing
the difference between the time of the rising or setting
of a body and six o'clock, or six hours from its meridian