The tropical zodiac, used in Western astrology, starts Aries at the spring equinox — a definition tied to Earth's seasons. The sidereal zodiac, used in Vedic astrology, anchors the signs to the fixed stars themselves. Two thousand years ago the two coincided. But Earth's axis traces a slow 25,800-year wobble — the precession of the equinoxes, about 50.3 arc-seconds per year — and the equinox point has been drifting backward through the constellations ever since.
That accumulated drift is the ayanamsa. On the Lahiri ayanamsa — the standard adopted by the Indian national calendar and the one BhagyaX computes with — the separation stands at 24°13′ as of mid-2026, widening slightly every year. Practical consequence: a planet at 10° Taurus tropically sits at roughly 16° Aries sidereally. This is why your 'sign' can legitimately differ between the two systems — and why neither system is in error.
Tropical astrology reads the Sun-Earth seasonal relationship and excels at psychological symbolism. Sidereal astrology reads positions against the actual stellar backdrop and pairs them with nakshatras and the Vimshottari dasha — the timing machinery Jyotish is known for. BhagyaX is a sidereal house: every chart is computed on Swiss Ephemeris with the Lahiri ayanamsa, and every claim in the reading traces back to a computed position and a classical rule.
Generate your free Vedic birth chart (Kundli) →
"NASA added a 13th sign." No — Ophiuchus is a constellation the ecliptic crosses, but both zodiacs are twelve equal 30° divisions by definition; constellations and signs are different objects. "My sign changed." Nothing changed — you simply read a sidereal value after a lifetime of tropical ones. "One system must be wrong." They measure from different anchors, like Celsius and Fahrenheit; the error would be mixing them mid-calculation, which is why BhagyaX states its frame — sidereal, Lahiri — on every reading.
Tropical fixes 0° Aries to the spring equinox; sidereal fixes the signs to the stars. Precession has separated the two frames by roughly 24 degrees today.
On the Lahiri ayanamsa it is 24°13′ as of June 2026, increasing by about 50.3 arc-seconds per year due to the precession of the equinoxes.
Sidereal, on the Lahiri (Chitrapaksha) ayanamsa — computed on Swiss Ephemeris and interpreted through 412 classical rules.
BhagyaX Worldwide: USA · UK · Canada · Australia · UAE · Singapore | The BhagyaX Method