Ayanamsa Systems

Ayanamsa is the angular difference between the tropical and sidereal zodiacs. The Asterwise API uses sidereal calculations throughout — the ayanamsa value determines the zodiac offset applied to all planetary positions.

Supported Values

Value	Name	Notes
lahiri	Chitrapaksha (Lahiri)	Default. Indian government standard. Used by the majority of Jyotish practitioners.
raman	B.V. Raman	Developed by B.V. Raman. Differs from Lahiri by approximately 0°22'. Common in South Indian traditions.
kp	Krishnamurti Paddhati (KP)	Used for KP system calculations. Differs from Lahiri by approximately 6'.
tropical	Tropical (Western)	Zero ayanamsa offset. Returns Western zodiac positions. Not recommended for Jyotish interpretation.

How to Pass Ayanamsa

Pass the ayanamsa field in any birth data request body. If omitted, lahiri is used.

{
  "date": "1985-11-12",
  "time": "06:45",
  "location": "Mumbai, India",
  "ayanamsa": "lahiri"
}

For matchmaking endpoints, set ayanamsa independently inside person1 and person2 objects.

Mean and True Ayanamsa

The ayanamsa grows steadily with precession (the mean ayanamsa) and also wobbles by up to about 19 arcseconds with nutation. Planetary positions from the ephemeris are apparent positions, which include nutation, so the value subtracted from them is the true ayanamsa: mean plus the nutation in longitude. This matches Swiss Ephemeris' own sidereal mode.

• Natal ayanamsa_value is the true ayanamsa used for that chart.
• GET /v1/astro/ayanamsha returns both: value_decimal (mean, the conventionally published figure) and true_value_decimal.

Until 2026-09-28 the natal, divisional, transit and matchmaking endpoints subtracted the mean value, which left positions off by the nutation (see the changelog).

Special Cases

Lal Kitab endpoints accept the ayanamsa field in the request schema but always use Lahiri internally. Passing any other value has no effect on the calculation.

KP endpoints (/v1/astro/kp/chart, /v1/astro/kp/significators, /v1/astro/kp/ruling-planets) are designed for use with "ayanamsa": "kp". Using a different value is technically accepted but will produce results inconsistent with KP methodology.

Recommendation

Use lahiri unless you have a specific reason to change it. All reference examples in this documentation use lahiri. If you are building a KP system feature, use kp. If you are building a hybrid Western/Vedic product, tropical returns Western positions through the same API surface.