Difference between Vedic and Western Astrology

The most easily referred to difference between the two lies in the method of measurement of the Zodiac. Vedic astrology uses primarily the sidereal zodiac (in which stars are considered to be the fixed background against which the motion of the planets is measured), whereas most Western astrology uses the tropical zodiac (the motion of the planets is measured against the position of the Sun on the Spring equinox). This difference becomes only noticeable over time, after the course of several centuries, as a result of the precession of the equinoxes. Synchronically, the two systems are identical, with just a shift of the origin of the ecliptic longitude by about 22 degrees or days, resulting on the placement of planets in the previous sign in Western charts about 80% of the time.