Nakṣatra and pāda calculation
How Lahiri sidereal lunar longitude is divided into 27 equal nakṣatras and four quarters each.
Calculation contract · released 2026-08-18
Definition
The implemented nakṣatra grid contains 27 equal sectors of 13⅓°; each sector contains four pādas of 3⅓°.
Calculation procedure
Convert Moon longitude to Lahiri sidereal longitude, divide by 360/27, floor to a sector, and divide its fractional position into four pādas.
Required inputs
- Moon tropical longitude
- Lahiri ayanāṁśa
- Boundary and normalization policy
Maha convention
Maha stores one-based index, name, pāda, fractional progress, and boundary sensitivity; Vimśottarī balance consumes the unrounded fraction.
Uncertainty and edge cases
Small ayanāṁśa or lunar-ephemeris differences can change a label near a nakṣatra or pāda boundary.
What this does not establish
Nakṣatra assignment is a chart convention; personality and timing claims require separate sourced rules and empirical status.
Authoritative references
These sources establish the calculation vocabulary, data product, or transformation convention. They do not establish astrological interpretation.
- Astronomy Engine
Don Cross (cosinekitty) · 2.1.19
Locally computed Sun and Moon positions derived from the VSOP87 and JPL-derived lunar theories, together with rise and set times, at the accuracy stated in the library documentation.
Boundary: Positions are computed in process rather than fetched from an authority, so a fact citing this source carries a digest over the computed values and not over a provider response body. Its accuracy is adequate for calendrical work and is not a substitute for a Horizons query where sub-arcsecond agreement matters.
- Swiss Ephemeris general documentation
Astrodienst AG · 2.10 documentation, checked 2026-08-18
An independent ephemeris implementation, supported reference choices, house calculations, and its dual-license boundary.
Boundary: Maha does not bundle or call Swiss Ephemeris in production. Frozen conformance results are validation evidence, not permission to redistribute its software or data.