Method

Planetary positions

Positions come from an implementation of the algorithms published in Jean Meeus, Astronomical Algorithms. Lunar longitude uses truncated ELP-2000/82 series terms. Planetary longitudes use Keplerian elements from JPL with perturbation corrections applied. Delta T follows the Espenak and Meeus polynomial fit.

The engine is written from published theory rather than adapted from an existing ephemeris library, which is why the site carries no licence obligation and costs nothing to run.

Ayanamsa

Lahiri, also called Chitrapaksha, anchored to 23 degrees 15 minutes 00 seconds at the vernal equinox of 21 March 1956, following the Indian Calendar Reform Committee definition. This matches Indian government publications and most Indian software.

Houses

Whole sign houses. The sign occupied by the ascendant becomes the whole of the first house, the next sign the second, and so on. This is the system described by Parashara and assumed by most Vedic practice.

The KP calculator will use Placidus cusps instead, because the KP system is built on them.

Divisions

The sixteen classical vargas follow the rules given in the Brihat Parashara Hora Shastra, including the odd and even sign variations that several of them require, and the two competing conventions for the D30 where the widely used Parashari form is applied.

Beyond the classical sixteen, the calculator will divide by any number you choose. These non classical divisions have no scriptural basis and are provided for exploration.

Checking the results

Every figure on this site can be verified against an independent source. Compare a sidereal longitude against a published panchang for the same moment, or against any ephemeris set to Lahiri. If you find a discrepancy larger than an arc minute that is not explained by a different ayanamsa or house system, we would like to hear about it.