Sidereal Zodiac

In the sidereal zodiac the signs of the zodiac are identical with the [[Star Constellation|star constellations]]. Western astrology generally works with the tropical zodiac which is calculated differently. The start of the tropical zodiac is precisely defined: It is the point at which the Sun crosses the celestial equator in a northerly direction on its apparent path around the Earth. There is no such clear definition in the sidereal zodiac which is used in Indian astrology. Another difference between the two zodiacs is that the precession causes the sidereal zodiac to move one degree every 72 years in relation to the tropical zodiac. The fairly standard ayanamsha value - which is the divergence between the two zodiacs - was 23 degrees, 51 minutes and 11 seconds on first of January 2000 (according to N.C. Lahiri). Using this value, 0 degrees of Aries in the tropical zodiac is equivalent to 6 degrees, 8 minutes and 49 seconds Pisces in the sidereal zodiac. However, some ayanamshas deviate from this value by several degrees.

Both the tropical and sidereal zodiacs are divided into twelve equal segments of 30 degrees, with the sequence of signs being identical.