The model — geo/helio duality, the Moon, eclipses, and the year
Click Run in Mandal to open the script live in
mandal.kaalshodh.com. Links are built from this page's own address, so they work wherever
this folder is hosted over HTTPS (same origin as Mandal, or a CORS-enabled host). Companion to the
Gol · Astro Lab tour.
Every tour here is self-paced: it stops at each step and holds the orrery still until you press Continue, so you can study the arrangement before it moves on.
what the observer's sky (Gol) cannot show directly
Toggle geocentric ↔ heliocentric — the śīghra epicycle is exactly this change of centre.
The 5°-tilted orbit crossing the ecliptic, and the slow regression of the line of nodes.
The Moon's apsides and its varying apparent size — the Moon's own manda inequality.
Golapāda IV.37–46 — the node made visible
Solar and lunar eclipses shown to fall only when the syzygy lands on a node.
Step one Saros at a time; the eclipse recurs at the same node every ~18 yr 11 d.
Kālakriyāpāda — the solar and lunar year, and precession
New-moon to new-moon against the Moon's return to the same star.
The Sun's ingress into each sign through the year; uttarāyaṇa and dakṣiṇāyana.
Months named for the full-moon's nakshatra, and the drift that forces adhimāsa.
The equinox drifting along the ecliptic, swept from 6000 BCE across the constellations.