The formula for computing the Ascendant is
Tan L = Sin E / cos E cosw – Sin w Tan A
The Ascendant is a point on the Celestial Horizon. The Eastern Celestial Horizon
First compute E, the Right Ascension of East Point, the East Point lying on the Celestial Equator and this E is subjected to the trignometric correction referred to as above.
The Celestial Horizon is known as Kshithija. w is the maximum declination of the Sun, The Soorya Parama Kranthi. A is the latitude of the place.
The Eastern Point on the Celestial Horizon is Udaya Lagna
180 degrees from it is the Astha Lagna or the Descendant