Sidereal zodiac — Astrology glossary

The sidereal zodiac measures planetary positions against the actual constellations as seen in the sky, fixing the signs to the background stars. It is the basis of Vedic (Jyotish) astrology and some Western siderealists. Because of precession, the slow wobble of Earth's axis, the sidereal zodiac has drifted roughly twenty-four degrees away from the tropical zodiac used in mainstream Western astrology, and that gap widens by about one degree every seventy-two years. The difference matters because it can shift a planet, or even the Sun, into the previous sign: someone born in late April who reads as a tropical Taurus is often a sidereal Aries. Sidereal astrologers apply a correction called the ayanamsha to convert tropical positions into sidereal ones.