as-cen-sion-al dif-fer-ence
Phonetic: /əˈsɛn.ʃə.nəl ˈdɪf.ər.əns/
In Medieval astrology, ascensional difference refers to the difference between the right ascension of a celestial body and its oblique ascension at a specific geographic latitude.
This concept was fundamental to Medieval astronomical and astrological calculation. Because zodiac signs rise at different speeds depending on latitude, the ascensional difference measures the variation between uniform equatorial rising and actual rising along the horizon. Medieval astrologers used ascensional differences in calculations involving house division, primary directions, planetary rising times, and predictive techniques. The doctrine reflects the close relationship between Medieval astrology and mathematical astronomy.