Methodology
How every chart is actually computed
We treat methodology as a feature, not a footnote. This page documents every astronomical and astrological choice that goes into the numbers you see on the site, with citations to classical sources.
1. Astronomical kernel
Planetary positions come from the Swiss Ephemeris, derived from NASA JPL's DE431 ephemeris. Accuracy is sub-arcsecond for modern dates. We compute true geocentric longitudes for the seven classical planets plus the mean lunar nodes (Rahu and Ketu).
Time inputs are normalized to UTC using the IANA tz database so daylight saving, war-time clock shifts and historical timezone changes are all handled correctly. A 1947 birth in Karachi, for example, resolves to the pre-Partition Indian timezone, not modern PKT.
2. Sidereal zodiac (ayanamsa)
Vedic astrology uses the sidereal zodiac, which tracks the actual position of constellations rather than the seasonally-anchored tropical zodiac. To convert from tropical longitudes (what Swiss Ephemeris returns) to sidereal we subtract the ayanamsa — the precessional offset.
Our default is Lahiri (Chitra Paksha), the value adopted by India's Calendar Reform Committee in 1955. It pins the fixed star Chitra (Spica) to 0 degrees of sidereal Libra. Roughly 24 degrees of precessional drift have accumulated since the reference epoch.
3. House system
We use Whole Sign houses: the entire sign occupied by the lagna (ascendant) becomes the first house, the next sign the second, and so on. This is the system described in the Brihat Parashara Hora Shastra and used by most traditional Indian astrologers. We do not compute Placidus or Koch houses — they are tropical innovations and misalign with classical Jyotish technique.
4. Dashas
The Vimshottari Mahadasha system is anchored to the lord of the nakshatra the Moon occupies at birth. The fraction of nakshatra already traversed at the birth moment determines how much of the first dasha has elapsed. From there we deterministically compute every Mahadasha, Antardasha and Pratyantardasha period out to age 120.
Period lengths follow the standard Parashari proportions and a 360-day year convention, which is why a printed dasha table will match our output to within hours.
5. Yogas and special combinations
Yoga detection runs deterministic rule checks against the natal chart — we never invent new yogas or rely on generative output. Coverage includes the Pancha Mahapurusha yogas, Raj yogas, Dhana yogas, Vipareeta Raj yogas, Kemadruma, Gajakesari and many others. Each yoga on the report carries a one-line rule statement so you can verify it against the source text yourself.
6. Compatibility (Ashtakoota)
We score the classical eight kootas (Varna, Vashya, Tara, Yoni, Graha Maitri, Gana, Bhakoot, Nadi) for a maximum of 36 points. We also flag Nadi Dosha and Bhakoot Dosha explicitly, because reducing a marriage decision to a single number is exactly the kind of misuse this tool should not encourage.
7. Daily forecast inputs
The daily forecast combines four classical signals against your natal chart: Chandrashtama (whether today's Moon transits the 8th house from your natal Moon), Tarabala (your 9-fold star strength for the day), current Mahadasha-Antardasha lord, and outer-planet transits over sensitive houses. No machine-learning models, no opaque scores.
Frequently asked
Which ephemeris do you use?+
The Swiss Ephemeris by Astrodienst — the same kernel used by JPL-grade research tools. It is accurate to within a few arcseconds for any date between 13,000 BCE and 17,000 CE.
Which ayanamsa is the default?+
Lahiri (Chitra Paksha), the official ayanamsa of the Indian government's Calendar Reform Committee and the most widely used value across South Asia. It places the fiducial star Chitra (Spica) at 0 degrees Libra.
Which house system do you use?+
Whole Sign houses — every sign is exactly one house, with the rising sign forming the first house. This is the system described in the Brihat Parashara Hora Shastra and used by most traditional Indian astrologers.
How are Vimshottari dashas computed?+
Dashas are derived from the longitude of the Moon at birth, mapped onto the 27 nakshatras. The total 120-year cycle is divided among the nine planets in the standard Parashari proportions (Ketu 7, Venus 20, Sun 6, Moon 10, Mars 7, Rahu 18, Jupiter 16, Saturn 19, Mercury 17).
What does compatibility scoring measure?+
Ashtakoota Guna Milan: eight kootas compared between two birth moons — Varna, Vashya, Tara, Yoni, Graha Maitri, Gana, Bhakoot and Nadi — for a maximum of 36 points. We surface the raw scores plus the deal-breakers (Nadi Dosha, Bhakoot Dosha) rather than just a single number.
Spotted a methodology bug? File an issue on GitHub and we'll fix it.