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In short
The sidereal zodiac is the circle of twelve signs and 27 nakshatras anchored to the fixed stars rather than to the equinox. It is the zodiac Vedic astrology and BPHS use. This app computes positions against the equinox first, then subtracts the Lahiri ayanamsa to put every graha and the Ascendant on the sidereal zodiac.
What the term means
A zodiac is the band of sky the Sun, Moon and planets move along, divided into twelve signs. The sidereal zodiac fixes where that division starts to the stars: 0° of Mesha is tied to a star-based reference, so a sign stays over the same stars. The tropical zodiac instead starts at the March equinox, which drifts slowly against the stars. The gap between the two is the ayanamsa. Every position in this app is sidereal.
Where the term comes from
BPHS builds the chart on a star-fixed frame without using the word. Ch. 3 Sl. 2-6 call the nakshatras the lights that do not move and lay the zodiac out as 27 nakshatras from Ashvini, the same circle divided into 12 rashis from Mesha, so the signs are measured against the stars. The translation uses "sidereal" once, in Ch. 28 Sl. 3-4, for the Sun's ordinary longitude, contrasting it with the Sun taken with the ayanamsa added. Advanced Predictive Astrology states that its author follows the Lahiri ayanamsa only.
How this app computes it
- The astronomical formulas return positions measured from the equinox of the birth date. One subtraction, the Lahiri ayanamsa for that date, turns each into a sidereal longitude. The node and the Ascendant go through the same step.
- For 19 January 1985, 11:14 IST, New Delhi, the ayanamsa is 23.64 degrees. The Sun moves from 299.10 to 275.46 (Capricorn 5.46), the Moon from 276.30 to 252.66 (Sagittarius 12.66), and the Ascendant from 16.68 to 353.04 (Pisces 23.04).
- Signs, nakshatras, padas, houses and every divisional chart are then read from the sidereal longitude only.
Pages that use this term
- Moon sign and nakshatra - a Vedic and a Western sign for the same Moon.
- Why apps disagree on your nakshatra - what changes between sidereal programs.
- Aries (Mesha Rashi) - the sidereal Aries against the tropical one.
- Mangal Dosha: what it is and is not - a rule read on sidereal positions.
- Ayanamsa calculator - the sidereal offset for any date.
- Methodology - the conversion worked through for one birth.
Related terms
- Nirayana - the Sanskrit-derived name for a sidereal position.
- Lahiri ayanamsa - the offset this app subtracts.
- Nakshatra - the star divisions the frame rests on.
- Longitude - the number that is converted.
Ayanamsa (Lahiri)
The gap between the tropical and sidereal zodiac, for any date you name - no birth details needed.
This date is sent only to compute the answer. Nothing is stored, no account is created, and no email is asked for.