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Jyotiṣa & Drik Gaṇita Compendium

Vedic Astronomy & Jyotiṣa Compendium

The mathematics and the algorithms behind Vedic calendrics (Panchanga Gaṇita). This compendium documents how the observational principle of dṛk-tulyatā is carried out with a modern ephemeris (the Swiss Ephemeris, on JPL DE431 data) and topocentric horizon models.

Siddhānta Śiromaṇi

Cited for: The principle this reference follows: a computation is corrected until it agrees with the sky as it is observed (dṛk-tulyatā). The tradition credits it to the siddhāntic astronomers, Bhāskara II among them.

The wording is not quoted here: the locus has not been checked against an edition.

Chapters in this Compendium

7 chapters

  • Core Ephemeris

    Astronomical Foundations & Drik Gaṇita

    The evolution from Siddhantic mean motions to modern Drik astronomy, the Saha/Lahiri Calendar Reform (1952–1955), and Swiss Ephemeris DE431 integration.

    Chapter 1

  • Electional

    Muhurta Mechanics & High-Stakes Timing

    The 30 diurnal and nocturnal muhurtas, Choghadiya, Rahu Kalam, the Dur Muhurtam weekday matrix, and the sectoral timing rules the engine encodes.

    Chapter 4

  • Phenomena

    Grahaṇam (Eclipses) & Sūtak Kaal

    Solar and lunar eclipse contact phases, magnitude and obscuration, the visibility rule (Dṛśya Niyama), and the ritual rules that depend on it.

    Chapter 5

  • Calendrics

    Sacred Calendars & 100-Year Birthdays

    Solar vs Luni-solar calendars, Amanta vs Purnimanta systems, Adhika/Kshaya Masa algorithms, and 100-year Hindu Tithi birthday calculation.

    Chapter 6

  • Verification

    Verification & Drik Parity

    What the engine's test suite checks, the two parity defects resolved against Drik Panchang's published method, and the city-by-city audit that has not been run.

    Chapter 7

Interactive Solilunar Playground

See the continuous angular mathematics in action across the 5 limbs of the Panchanga.

Panchanga limb sandbox

Illustration, not the engine

Move either longitude and watch the three limbs that follow from them. This classifies a single instant; the engine additionally solves for the moment each limb ends, which is the figure an almanac actually publishes.

Tithi — (Moon − Sun) mod 360, ÷ 12°
Saptamī#7
Śukla pakṣa (waxing) · elongation 82.70° · 89% elapsed
Nakṣatra — Moon ÷ 13°20′
Maghā
#10 · pāda 3
Yoga — (Sun + Moon) mod 360, ÷ 13°20′
Harṣaṇa
#14