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The ayanamsa is a single number that explains most of the difference between a Vedic chart and a Western one. It is the angle between the tropical zodiac, measured from the equinox, and the sidereal zodiac, measured from the fixed stars. Enter any date and this gives you the Lahiri value for it. No birth details are needed, because the ayanamsa depends on the date alone.
The Earth's axis wobbles like a slowing top, one full circle in about 25,800 years. That wobble drags the equinox slowly backwards through the constellations, roughly fifty seconds of arc a year. Around the fourth century the equinox sat close to the start of sidereal Aries and the two zodiacs agreed. Every year since, they have separated a little further, and the accumulated separation is the ayanamsa.
There is more than one ayanamsa, because there is more than one opinion about exactly when the two zodiacs coincided. Lahiri, also called Chitrapaksha, fixes the reference by the star Spica and is the standard used across India and by the government's calendar reform committee. Raman and Krishnamurti values differ from it by a few minutes to a degree or so. This site uses Lahiri throughout, which is worth knowing if you compare a chart here against one cast elsewhere.
For a Sun sign, almost nothing — you would need a birth within a few hours of a sign change for the choice of ayanamsa to matter. For a nakshatra it starts to matter, for a navamsa it matters more, and for a KP sub lord it can be decisive. That is the honest hierarchy: the finer the division, the more the choice of ayanamsa shows up in the answer.
It does not tell you that sidereal is right and tropical is wrong, or the reverse. Both systems are coherent within themselves and each has centuries of practice behind it. What the ayanamsa does explain is why the same birth produces two different charts, which is a question with an actual answer rather than an argument.
The Earth's axis wobbles like a slowing top, one full circle in about 25,800 years. That wobble drags the equinox slowly backwards through the constellations, roughly fifty seconds of arc a year. Around the fourth century the equinox sat close to the start of sidereal Aries and the two zodiacs agreed. Every year since, they have separated a little further, and the accumulated separation is the ayanamsa.
There is more than one ayanamsa, because there is more than one opinion about exactly when the two zodiacs coincided. Lahiri, also called Chitrapaksha, fixes the reference by the star Spica and is the standard used across India and by the government's calendar reform committee. Raman and Krishnamurti values differ from it by a few minutes to a degree or so. This site uses Lahiri throughout, which is worth knowing if you compare a chart here against one cast elsewhere.
For a Sun sign, almost nothing — you would need a birth within a few hours of a sign change for the choice of ayanamsa to matter. For a nakshatra it starts to matter, for a navamsa it matters more, and for a KP sub lord it can be decisive. That is the honest hierarchy: the finer the division, the more the choice of ayanamsa shows up in the answer.
It does not tell you that sidereal is right and tropical is wrong, or the reverse. Both systems are coherent within themselves and each has centuries of practice behind it. What the ayanamsa does explain is why the same birth produces two different charts, which is a question with an actual answer rather than an argument.
The angle between where the zodiac starts for Western astrology and where it starts for Vedic astrology. It is currently about twenty-four degrees and grows by roughly fifty seconds of arc every year.
Because it measures a drift, not a constant. The Earth's axial precession moves the equinox backwards against the stars continuously, so the gap between the two zodiacs is a little larger every year.
Lahiri, unless you have a specific reason not to. It is the Indian standard and what most Vedic software and almanacs use. KP practitioners use the KP ayanamsa, which differs slightly and can move a borderline sub lord.
No. The ayanamsa depends only on the date, and it changes so slowly that the time of day makes no practical difference to the value.
ShukrAI computes from your real birth chart with the Swiss Ephemeris and Lahiri ayanamsa. It is for reflection and self-understanding, is never a prediction of doom, and is not a substitute for professional advice.
