Drik Ganita · Lahiri Ayanamsa · VSOP87 planetary theory.

Most online astrology platforms treat their computational layer as a black box. You enter your birth details, you get a chart back, and you have no way to verify what algorithms produced it. VedHoroscope takes the opposite approach. Every astronomical calculation is documented, every standard we use is publicly verifiable, and every number on the platform can be independently cross-checked against published ephemeris data.

This page explains exactly how we compute panchang, planetary positions, kundli charts and rashifal predictions. We follow the Drik Ganita standard with Lahiri Ayanamsa — the official Government of India reference for Vedic astronomical computation.

At the foundation of every calculation is VSOP87 (Variations Séculaires des Orbites Planétaires), the analytical planetary theory developed by Pierre Bretagnon and Jean-Louis Simon at the Bureau des Longitudes, Paris. VSOP87 represents planetary motion as trigonometric series in time, providing heliocentric ecliptic coordinates of all planets with precision better than one arc-second over centuries.

For each request, our engine computes the heliocentric longitude, latitude and radial distance of the Sun, Moon, Mars, Mercury, Jupiter, Venus and Saturn at the requested instant. These are then transformed to geocentric apparent coordinates by accounting for light-time correction, aberration and nutation.

Rahu and Ketu — the lunar nodes considered shadow planets in Vedic astrology — are computed as the Moon's mean ascending and descending nodes, completing the nine-Graha set required for Jyotish.

Modern astronomical computation produces tropical (seasonal) coordinates referenced to the moving vernal equinox. Vedic astrology requires sidereal coordinates — fixed against the actual stars. The difference between the two is the Ayanamsa.

VedHoroscope uses the Lahiri Ayanamsa (also called Chitrapaksha Ayanamsa), named after astronomer Nirmal Chandra Lahiri. This is the official sidereal standard adopted by the Indian Government's Calendar Reform Committee in 1955 and used by the Positional Astronomy Centre, Kolkata for the Indian Astronomical Ephemeris and the Rashtriya Panchang.

For example, on 1 January 2026 the Lahiri Ayanamsa is approximately 24°13′. To convert any tropical longitude to its Vedic sidereal counterpart, the engine subtracts this value. This correction is applied uniformly to every planet, every house cusp, and every transit calculation across the platform.

All five limbs of the panchang are derived from the underlying sidereal positions of the Sun and Moon:

A natal Kundli requires four inputs: date, time, latitude, and longitude of birth. The engine first computes the Julian Day Number in Universal Time, applies the deltaT correction for terrestrial time, then computes:

• Sidereal longitudes of all nine Grahas at the birth instant
• The Lagna (Ascendant) — the sidereal degree rising on the eastern horizon, computed from local sidereal time and birth latitude
• Bhava (house) cusps using the equal-house system from the Lagna (the traditional Vedic approach)
• Vimshottari Dasha sequence and current period — calculated from the Moon's exact Nakshatra and pada at birth, following the 120-year cycle assignments in Brihat Parashara Hora Shastra
• Divisional charts (Vargas) including Navamsa (D9), derived from sub-divisions of the natal Rashis

Every chart is computed from first principles for the exact birth instant — no lookup tables, no rounding to the nearest hour, no approximations.

Daily, weekly, monthly and yearly Rashifal is generated by a rule-based Vedic prediction engine, not by a generic AI text model. The engine combines four streams of authentic Jyotish data:

The engine combines these four streams using sentence templates grounded in traditional Jyotish vocabulary, then renders the final prediction in both Hindi and English. Because planets move every day, the prediction changes naturally — there are no recycled templates and no generic horoscope copy.

Because we follow the Drik Ganita + Lahiri Ayanamsa standard, our data should match any other source that follows the same standard. Specifically:

• Indian Astronomical Ephemeris (published by the Positional Astronomy Centre, Kolkata) — Tithi and planetary positions should agree to within seconds of arc.
• Rashtriya Panchang (Government of India) — the official panchang published yearly. Tithi and Nakshatra start times should match.
• NASA JPL Horizons — for raw heliocentric and geocentric planetary coordinates (before sidereal conversion).
• DrikPanchang.com — also follows Drik Ganita + Lahiri Ayanamsa. Direct comparison should match.

• Brihat Parashara Hora Shastra — Maharishi Parashara. Foundational text for natal chart interpretation, Vimshottari Dasha and house lordships.
• Surya Siddhanta — classical Indian astronomical treatise. Reference for traditional planetary motion and panchang construction.
• Phaladeepika — Mantreshwar. Reference for predictive yogas and combinations applied in the Rashifal engine.
• Indian Astronomical Ephemeris — Positional Astronomy Centre, IMD, Kolkata. Reference for Lahiri Ayanamsa values and panchang verification.
• Planetary Programs and Tables from -4000 to +2800 — P. Bretagnon & J.-L. Simon (1986). The published VSOP87 theory underlying our planetary computations.
• Astronomical Algorithms — Jean Meeus. Reference for nutation, aberration, sidereal time and sunrise/sunset equations.