Evidence you can replay

Accuracy and Reproducibility

AstroAPI exposes the conventions and fingerprints behind a result. Public comparison summaries, a machine-readable vector set, pinned ephemeris and timezone versions, normalized inputs, fact source paths, and SHA-256 calculation identifiers make integrations easier to audit.

Download test vectorsRead methodology

Measured comparisons

Tropical planets
310 samples; maximum observed difference 1.4 arcseconds
Chart angles
2,325 location/time cases; Ascendant below 9 arcseconds, MC below 2.2
Sidereal planets
930 samples across three modes; maximum observed difference 19 arcseconds

The dated comparisons use independent Swiss Ephemeris/Moshier outputs as offline reference data. Swiss software and data are not runtime dependencies. These figures describe the enumerated samples, not a universal error bound.

What customers can reproduce

  • The public vector file identifies the input, expected values, tolerance, comparison design, and SHA-256 of each underlying committed evidence set.
  • Calculation responses state their zodiac, ayanamsa, house model, frame, and other route-specific conventions rather than implying interchangeability with another engine.
  • POST /api/astro/natal-context produces deterministic JSON, XML, or Markdown fact bundles with stable fact IDs, source paths, a calculation hash, and artifact hashes.
  • Place and time resolution identifies GeoNames snapshot 2026-10-02, IANA tzdb 2026d, and Python tzdata 2026.4.

Interpret the evidence correctly

A deterministic result can still differ from another product because of ephemeris, frame, Earth-orientation, historical timezone, house-system, boundary, or rounding choices. The evidence supports reproducibility of AstroAPI's declared model; it is not scientific certification, practitioner approval, or predictive validation.