Documentation

Caelus is an MIT ephemeris engine: planetary positions, houses, aspects, and astronomical events, with no ephemeris files on disk.

New here? Start with the Quickstart, then read Computing Charts. The full package surface is in the API Reference.

Install caelus and compute your first chart in the browser or Node.

The chart object: bodies, angles, cusps, aspects, and the UT vs local-time hazard.

How the four packages compose end to end: birth time, engine, wheel, and MCP.

Twelve house systems, tropical and sidereal modes, and polar fallbacks.

Returns, progressions, solar arc, composite, Davison, harmonics, dignities, and sect.

Embedded vs Node loader: what ships in the bundle and what loads lazily.

Add nine chart tools to Claude, Cursor, and other MCP clients.

Transits, the when() query language, event search, and chart wheels.

Scan a window with rankMoments, score each instant with the electional primitives, and render the winning chart.

Beyond the flat wheel: a 3D chart sphere, an astrocartography world map, and a graphic ephemeris, rendered live.

Generated reference for the caelus package surface.

Date range, polar fallback, civil-time hazards, longitude convention, and the versioning contract.

A full Next.js app: birth form, timezone handling, chart wheel. Clone and deploy.

Release notes for all four packages, versioned in lockstep.