How AstroYogam Is Validated

Most astrology apps claim 'accuracy' without stating ayanamsa, sunrise definition, or Moon coordinate frame. AstroYogam is different: pinned conventions are public, tests live in the repo, and the ephemeris layer is a separate open-source service.

Trust is not a slogan - it is a calculation you can re-check. What follows is not marketing copy; it is how the production engine actually runs.

Lahiri (Chitrapaksha) ayanamsa: the sidereal zodiac measure. In Swiss Ephemeris this is SIDM_LAHIRI. Every rasi, nakshatra, and tithi boundary rests on it.

Sunrise-anchored panchangam: in the Tamil civil day tradition, a day starts at local sunrise. Limbs such as tithi and nakshatra are taken with respect to that sunrise for the day's assignment.

Sunrise definition: disc-center with atmospheric refraction - the combination that matches trusted almanacs.

Moon: geocentric coordinates. Topocentric correction is deliberately off; it would shift nakshatra padas relative to Drik Panchang.

Time: historical IANA timezone rules, including pre-1947 India and LMT for older dates. A single modern UTC offset is not enough for birth charts.

Our ground truth is Drik Panchang (drikpanchang.com). For selected dates and places, engine output is checked against that almanac. If a convention changes, golden tests must be updated - silent drift is not allowed.

Every engine change must pass this net. 'Looks right' is not enough; values must match prior pins or be intentionally re-pinned with a documented convention change.

Planetary longitudes, rise/set, and boundary root-finding come from a separate open-source service, swisseph-service (Swiss Ephemeris / pyswisseph, AGPL-3.0). AstroYogam calls it over HTTP - never imports it in-process - so the licensing boundary stays clean.

That service's README names AstroYogam as the consuming product. The computation layer is inspectable; the product experience and narration live in the app.

The Gemini-powered narration layer only receives structured data the engine already computed. It does not calculate a planet, invent a date or time, or assert an astrological fact the engine did not produce. If the engine did not compute it, the honest answer is 'not computed yet' - never a guess.

That matters for AI-skeptical readers and for answer engines that cite pages: the numbers are deterministic; the language is explanatory.

v1 scope: Rasi (D1) + Navamsa (D9); nine grahas plus Lagna; the five panchangam limbs plus sunrise/sunset; South Indian chart grid; Tamil and English.

Not yet fully computed or published as engine truth: other divisional charts, a full muhurta rule engine for wedding-date lists, and North Indian chart style. We will not publish those as if the engine produced them.