Equatorial ascendant


In astrology, the Equatorial Ascendant, or the East Point, is the sign and degree rising over the Eastern Horizon at the Earth's equator at any given time. In the celestial sphere it corresponds to the intersection of the ecliptic with a great circle containing the celestial poles and the East point of the horizon.

Calculation

Equations derived from spherical trigonometry allow for the conversion from equatorial coordinates to ecliptic coordinates. As points in the ecliptic have no latitude and the East point of the horizon has a right ascension 6h higher than that of the meridian, the equation that determines East Point's longitude can be written as:
where is the local sidereal time and is the obliquity of the ecliptic. The equation can also be derived from the Ascendant at the equator.