Sidereal Zodiac

Refers to the position of the celestial bodies as seen against the actual constellations not the signs. The starting point for Aries is therefore unreliable because of precession and the 'natural zodiac' can be disputed. Western sidereal astrologers use the value of the SVP (Synetic Vernal Point) specified by Fagan and Allen, which defines the mean longitude of the Vernal Point of the epoch BY1950.0 to be exactly 335?°57'28.64", which is equivalent to stating that its Ayanamsha is 24?°02'31.36". The Fagan-Allen determination leads to a Zodiac which is identical to that used by ancient astrologers (Egyptian, Babylonian, Persian, Arabian, Magi). Its use has been established to within 0.1?° for the period BC786-AD500, and to within less than 5?° as early as BC2767. All ancient astrologers used the same Sidereal Zodiac, but its universality diminished from the time of Claudius Ptolemy (about 75AD) until its re-discovery by Cyril Fagan in our century. Modern Hindu Astrology, which is clearly derived from Greek sources after the Alexandrian conquests which followed his rise to power in BC336, and reflect much of the work of Ptolemy, uses one of a set of Ayanamshas, which yield coordinate systems some of which are only approximately fixed with reference to the stars.