Analyzing the Validity of Nadi Coordinates Using Astrology Software for Marital Predictions

Abstract

In Ashtakoota horoscope matching, Nadi koota carries 8 of the 36 points, and a same-Nadi result (Nadi dosha) is often taken as a reason to turn down a marriage proposal. The verdict rests on a single computed value: the sidereal longitude of the Moon at each partner's birth, as returned by astrology software. This study asks whether that value is stable enough to support a marital prediction. We generated 20,000 birth instants between 1970 and 2005 at ten Indian cities. For each one we computed the Moon's longitude with two independent ephemeris engines, five ayanamsa conventions, geocentric and topocentric positions, and birth-time shifts of 5 to 60 minutes.

The two engines agreed to within 32 arcseconds and changed only 0.02% of Nadi assignments. Software conventions mattered far more. Moving from the Lahiri to the Raman ayanamsa changed the Nadi of 8.0% of individuals and reversed the Nadi dosha verdict for 9.9% of 10,000 simulated couples (Cohen's κ = 0.77). Topocentric correction changed 3.1% of Nadi assignments, about as many as a 60-minute error in birth time (3.0%). In a Monte Carlo analysis, verdict disagreement at this level reduced a true odds ratio of 2.0 to about 1.7 and lowered statistical power from 0.64 to 0.43 in a sample of 300 couples. A Nadi verdict therefore depends partly on how the software is set up. Any empirical test of Nadi-based marital prediction has to fix and report these settings before its outcome data can be read.