Ayanamsa is the Sanskrit term for the longitudinal difference
between the tropical or Sayana and sidereal or Nirayana zodiacs.
It is defined as the angle by which the sidereal ecliptic
longitude of a celestial body is less than its tropical ecliptic
longitude.    Today's astronomical calculations always use
tropical longitudes, but certain schools of astrology, notably
the Vedic school of astrology use sidereal longitude. Hence,
when the proponents of these schools of astrology use modern
astronomical calculations to determine the position of celestial
bodies, they need to take into account the difference caused by
the different reference point used in specifying the longitude,
and this they call the ayanamsha.  But all orthodox schools of
Vedic astrology reject modern astronomy and still base their
computations upon traditional texts and treatises, mostly
following Surya Siddhānta or treatised based on it. Some of them
do it out of habit, while others argue that modern astronomy
deals with material objects w