The Zodiac Software was developed according to the principles of Vedic Spherical Astronomy & Trignometry.
The longitudes measured along the Ecliptic are called true longitudes and the longitudes measured along the Vishuvat Vritta, the Celestial Equator, are known as Right Ascension.
When we say the Right Ascension of East Point, we mean the East Point along the Celestial Equator. The Right Ascension of the Meridian Cusp( RAMC ), is the longitude of the MC or Mid Heaven measured along the Celestial Equator.
The formula for computing the MC , the Madhya Lagna is as follows
tan K = tan R /cos w
where is the K is the longitude of the MC, and R, Sidereal Time converted into degrees.
180 degrees from the Madhya Lagna or the MC is the IC, the Imum Caeli or Patala Lagna.