The difference between the Right Ascension of any body and its Oblique Ascension: used chiefly as expressing the difference in time between the rising or setting of a celestial body, and six o'clock; or, six hours from the meridianal passage. To find this, add the log. tangent of the declination of the planet, to the log. tangent of the latitude of the place. The sum will be the log. sine of the Ascensional Difference. This added to the planet's Right Ascension, when in South declination (or subtracted, when in North declination), gives the Oblique Ascension of the planet. The reverse process yields the Oblique Descension.
ASTROLABE ENCYCLOPEDIA
