caelus-engine

The Python reference implementation for Caelus astrology computation. Clean-room, MIT-licensed, written from published sources (VSOP87D, ELP/Meeus, IAU models, JPL Horizons fits). No Swiss Ephemeris code, no bundled third-party ephemeris files.

The engine reads pre-built Chebyshev and series packs shipped with the package and runs on the Python standard library alone. It is also the reference that the TypeScript engine (caelus on npm) is pinned to by a golden conformance suite.

Install

pip install caelus-engine

The import package is astroengine:

from astroengine import Engine, BODIES

eng = Engine("full")
jd = 2451545.0  # 2000-01-01 12:00 UT
for body in BODIES:
    print(f"{body:10s} {eng.longitude(body, jd):10.5f}")

What it computes

Planetary and lunar apparent geocentric ecliptic longitudes (VSOP87D for the planets, Meeus Ch. 47 for the Moon, Meeus Ch. 37 series for Pluto), with light-time, annual aberration, FK5 frame correction, and IAU 1980 nutation.
12 house systems; tropical and sidereal (7 ayanamsas).
Aspects with configurable orbs.
Events: rise/set/transit, longitude crossings, lunar phases, stations, Gauquelin sectors, solar and lunar eclipses.
Fixed stars and topocentric positions.
Derived charts: returns, secondary progressions, solar arc, composite and Davison, harmonics, antiscia, declination aspects and parallels, out-of-bounds, dignities, sect.
Electional primitives: applying/separating aspects, solar phase (cazimi/combust/under-the-beams), planetary hours, void-of-course Moon, house placement.
A declarative when() query engine over celestial predicates.
A turbo tier (Turbo): segmented Chebyshev longitude packs fit to the engine for bulk scans.
3D aspects (angular_separation_3d): the great-circle angle between two bodies, accounting for ecliptic latitude.
Astrocartography (astrocartography): the planetary angle lines (MC/IC meridians, ASC/DSC rising and setting tracks) across the globe.

Accuracy

Accuracy is calibrated against Swiss Ephemeris and validated against JPL Horizons, stated per body rather than as a blanket figure. See the validation tables at https://ephemengine.com.

Optional: the fitting toolchain

The engine runs without any third-party dependency. The data-fitting tools that regenerate the coefficient packs need numpy:

pip install "caelus-engine[fit]"

License

MIT. See LICENSE. Project home: https://ephemengine.com. Source: https://github.com/heavyblotto/caelus.

Download files

Download the file for your platform. If you're not sure which to choose, learn more about installing packages.

Source Distribution

caelus_engine-0.24.0.tar.gz (27.7 MB view details)

Uploaded Aug 15, 2026 Source

Built Distribution

If you're not sure about the file name format, learn more about wheel file names.

The dropdown lists show the available interpreters, ABIs, and platforms. Enable javascript to be able to filter the list of wheel files.

caelus_engine-0.24.0-py3-none-any.whl (28.0 MB view details)

Uploaded Aug 15, 2026 Python 3

File details

Details for the file caelus_engine-0.24.0.tar.gz.

File metadata

Download URL: caelus_engine-0.24.0.tar.gz
Upload date: Aug 15, 2026
Size: 27.7 MB
Tags: Source
Uploaded using Trusted Publishing? Yes
Uploaded via: twine/7.0.0 CPython/3.13.14

File hashes

Hashes for caelus_engine-0.24.0.tar.gz
Algorithm	Hash digest
SHA256	`aa7dd981a788771cc898b0d882b420e28f1a85767cad45cce802b49a1b901f09`
MD5	`9dc1269a007f031cde553b3acfee9269`
BLAKE2b-256	`e933ff40a9062f055eb2552674fb796a8ea9ad373c1ea81fad3a7b123b9970ef`

See more details on using hashes here.

Provenance

The following attestation bundles were made for caelus_engine-0.24.0.tar.gz:

Publisher: release.yml on heavyblotto/caelus

Attestations: Values shown here reflect the state when the release was signed and may no longer be current.

Statement:
- Statement type: https://in-toto.io/Statement/v1
- Predicate type: https://docs.pypi.org/attestations/publish/v1
- Subject name: caelus_engine-0.24.0.tar.gz
- Subject digest: aa7dd981a788771cc898b0d882b420e28f1a85767cad45cce802b49a1b901f09
- Sigstore transparency entry: 2477259626
- Sigstore integration time: Aug 15, 2026
Source repository:
- Permalink: heavyblotto/caelus@322250c77e8642bcf5e2fb2e34d1a4d6e4185643
- Branch / Tag: refs/tags/v0.24.0
- Owner: https://github.com/heavyblotto
- Access: public
Publication detail:
- Token Issuer: https://token.actions.githubusercontent.com
- Runner Environment: github-hosted
- Publication workflow: release.yml@322250c77e8642bcf5e2fb2e34d1a4d6e4185643
- Trigger Event: push