Ayanamsa

The ayanamsa is the angle between the tropical zodiac (tied to the seasons) and the sidereal zodiac (tied to the fixed stars) at a given moment. Subtracting it from a tropical position gives the sidereal position Vedic astrology uses.

Western and Vedic astrology compute the same planetary positions — they disagree only on where zero degrees of Aries sits. Western astrology uses the tropical zodiac, anchored to the spring equinox. Vedic (Jyotish) uses the sidereal zodiac, anchored to the fixed stars. Because the equinox slowly drifts against the stars — the precession of the equinoxes, about 50 arcseconds a year — the two zodiacs pull apart over time. The gap between them at a given date is the ayanamsa. There are several definitions; this reading uses the Lahiri (Chitrapaksha) ayanamsa, the standard in modern Indian astrology, currently around 24°. To produce a sidereal chart, we take each tropical longitude we already computed and subtract the ayanamsa. Nothing is re-observed — the sky is the same — the zodiac is simply re-anchored. The ayanamsa itself is a real, computed quantity: it follows directly from the precession of the equinoxes, which is measured astronomy. What the resulting sidereal placements mean is interpretation, the same as any zodiac.

Not: The ayanamsa is not a matter of one zodiac being correct and the other wrong. It is a coordinate offset between two conventions for numbering the zodiac. Different ayanamsa definitions (Lahiri, Raman, Krishnamurti) differ by a fraction of a degree; this reading states which one it uses.

The ayanamsa is exact astronomy — it is the accumulated precession. The disagreement between Western and Vedic readings that follows from it is a disagreement of interpretive convention, not of measurement.