Which Engine Actually Computes Your Charts?

Every astrology API rests on an ephemeris: the engine that computes where the planets were at a given moment. Everything else — houses, dashas, yogas, predictions — depends on those positions being right. When you choose an astrology API, you are also, often invisibly, choosing whose ephemeris you trust. This page makes that choice visible.

Swiss Ephemeris is genuinely excellent. It is the long-standing standard in astrology software, derived from NASA's Jet Propulsion Laboratory ephemeris data, and it powers Astro.com along with a large share of professional desktop tools and APIs. It is precise, well-maintained and battle-tested over decades. If an API is built on Swiss Ephemeris, its raw positions are in good hands.

Its one structural characteristic, for a developer's purposes, is that it is a closed third-party library consumed under licence. That is not a flaw — it is simply a fact that shapes what you, the integrator, can and cannot independently verify.

Prokerala's calculations build on the Swiss Ephemeris. That is a sound foundation, and it is part of why Prokerala's Vedic computation is reliable. The nuance worth naming is that Prokerala — like most astrology APIs — consumes the engine rather than owning it. When you use Prokerala, you are trusting Prokerala's integration of a closed library you cannot inspect end to end.

Vedika took a different path. Rather than reselling a third-party library, Vedika built its own astronomical engine, XALEN Ephemeris, and open-sourced it under Apache-2.0 — published on crates.io (xalen), PyPI (xalen) and npm (@xalen/wasm), with roughly 2,200 tests.

Crucially, it is verified the same way the professionals verify: validated against the public JPL DE440 reference ephemeris and the industry-standard swetest tool, with sub-arcsecond agreement, and no chart in a reproducible JPL DE440 benchmark deviating beyond 0.1°. Because the engine is open, those checks are not a promise you have to take on faith — you can run them yourself.

If your only concern is accurate raw positions, an API built on Swiss Ephemeris — Prokerala among them — will serve you well; the engine is excellent. Choose Vedika when you also want control and verifiability: an engine you can audit, reproduce and reason about, instead of a closed dependency several layers below your code. On top of that auditable engine, Vedika adds the layers competitors do not — three astrology systems in one API, and a built-in natural-language query endpoint.