ketu 0.2.1

Library to compute astronomical bodies positions and planetary aspects between them

Ketu

Vous préférez le français ? Consultez README.md

Ketu is a lightweight Python library for computing the positions of astronomical bodies (Sun, Moon, planets, and the mean Node a.k.a. Rahu) and generating calendars driven by astrological aspects.

This library was originally designed to generate biodynamic calendars and time series based on astrological aspects. It can be used as a basis for building astrology software.

Features

• Planetary positions for 13 bodies (Sun, Moon, Mercury, Venus, Mars, Jupiter, Saturn, Uranus, Neptune, Pluto, Rahu/Mean Node, True North Node, Lilith)
• Detection of the 7 major aspects (Conjunction, Semi-sextile, Sextile, Square, Trine, Quincunx, Opposition)
• Retrogradation detection and planet motion helpers
• Time system conversions (UTC, Julian Day)
• Orb system based on Abu Ma'shar (787-886) and Al-Biruni (973-1050)
• Interactive CLI for a non-programmatic workflow
• Python API that fits into your own tooling

Installation

From PyPI (recommended)

pip install ketu

From source

git clone https://github.com/alkimya/ketu.git
cd ketu
pip install -e .

Quick Start

Interactive mode (CLI)

Run the command below and answer the prompts:

ketu

You will be asked for:

• A date (ISO format: 2020-12-21)
• A time (ISO format: 19:20)
• A timezone (for example Europe/Paris)

The program prints:

• Positions of every celestial body with zodiac signs
• All inter-planet aspects with their orbs

Programmatic usage

from datetime import datetime
from zoneinfo import ZoneInfo
import ketu

# Define a datetime
dtime = datetime(2020, 12, 21, 19, 20, tzinfo=ZoneInfo("Europe/Paris"))
jday = ketu.utc_to_julian(dtime)

# Display planetary positions
ketu.print_positions(jday)

# Display aspects
ketu.print_aspects(jday)

Additional examples

Compute a planet position

from datetime import datetime
from zoneinfo import ZoneInfo
import ketu

dtime = datetime(2024, 10, 26, 12, 0, tzinfo=ZoneInfo("UTC"))
jday = ketu.utc_to_julian(dtime)

sun_long = ketu.long(jday, 0)
print(f"Sun longitude: {sun_long:.2f}°")

sign, deg, mins, secs = ketu.body_sign(sun_long)
print(f"Position: {ketu.signs[sign]} {deg}°{mins}'{secs}\"")

Check whether a planet is retrograde

import ketu

# Mars (body id = 4)
if ketu.is_retrograde(jday, 4):
    print("Mars is retrograde")
else:
    print("Mars is direct")

Calculate all aspects for a given day

import ketu

aspects_data = ketu.calculate_aspects(jday)

for aspect in aspects_data:
    body1, body2, i_asp, orb = aspect
    print(f"{ketu.body_name(body1)} - {ketu.body_name(body2)}: "
          f"{ketu.aspects['name'][i_asp].decode()} (orb: {orb:.2f}°)")

Documentation

The full documentation is hosted on Read the Docs (French by default, English via the language toggle).

Included sections:

• Installation: detailed setup instructions
• Quickstart: guided tour of the basics
• Concepts: astrological and astronomical background
• API Reference: all functions documented
• Examples: advanced usage patterns

Requirements

• Python 3.10 or higher
• numpy ≥ 1.20.0 — numerical routines and arrays
• pyswisseph ≥ 2.10.0 — Swiss Ephemeris bindings

The dependency on pyswisseph is scheduled for removal in a future release, replaced by pure NumPy implementation.

Supported bodies

Body	ID	Orb	Average speed (°/day)
Sun	0	12°	0.986
Moon	1	12°	13.176
Mercury	2	8°	1.383
Venus	3	10°	1.200
Mars	4	8°	0.524
Jupiter	5	10°	0.083
Saturn	6	10°	0.034
Uranus	7	6°	0.012
Neptune	8	6°	0.007
Pluto	9	4°	0.004
Rahu (Mean Node)	10	0°	-0.013
True North Node	11	0°	-0.013
Lilith (Black Moon)	12	0°	-0.113

Supported aspects

Aspect	Angle	Orb coefficient
Conjunction	0°	1
Semi-sextile	30°	1/6
Sextile	60°	1/3
Square	90°	1/2
Trine	120°	2/3
Quincunx	150°	5/6
Opposition	180°	1

Roadmap

• Removal of dependency on pyswisseph
• Pure numpy implementation of planetary calculations
• Search for exact aspects between two dates
• Generation of aspect calendars
• API for progressions and directions
• Support for more celestial bodies (asteroids, etc.)

Contribution

Contributions are welcome! Feel free to:

• Open an issue to report a bug or suggest a feature
• Submit a pull request
• Improve the documentation

See CONTRIBUTING.md for more details.

License

This project is licensed under MIT. See the LICENSE file for more details.

Contact

Loc Cosnier - @alkimya

Project: https://github.com/alkimya/ketu