practical-astronomy-python

Algorithms from Practical Astronomy with your Calculator or Spreadsheet by Peter Duffett-Smith, implemented in Python 3. API documentation is published here.

If you're interested in this topic, please buy the book! It provides far more detail and context.

Quick Start

Install:

pip install practical-astronomy

Create easter.py:

import practical_astronomy.pa_datetime as pd
 
print(pd.get_date_of_easter(2024))

Run it:

python easter.py

Result:

(3, 31, 2024)

Unit Tests

If you clone the repo locally, you can run unit tests with the Make utility:

make all-tests

Library Functions

Documentation here.

Date/Time

Type	Description
Calculate	Date of Easter
Convert	Civil Date to Day Number
Convert	Greenwich Date <-> Julian Date
Convert	Julian Date to Day-of-Week
Extract	Day, Month, and Year parts of Julian Date
Convert	Civil Time <-> Decimal Hours
Extract	Hour, Minutes, and Seconds parts of Decimal Hours
Convert	Local Civil Time <-> Universal Time
Convert	Universal Time <-> Greenwich Sidereal Time
Convert	Greenwich Sidereal Time <-> Local Sidereal Time

Coordinates

Type	Description
Convert	Angle <-> Decimal Degrees
Convert	Right Ascension <-> Hour Angle
Convert	Equatorial Coordinates <-> Horizon Coordinates
Calculate	Obliquity of the Ecliptic
Convert	Ecliptic Coordinates <-> Equatorial Coordinates
Convert	Equatorial Coordinates <-> Galactic Coordinates
Calculate	Angle between two objects
Calculate	Rising and Setting times for an object
Calculate	Precession (corrected coordinates between two epochs)
Calculate	Nutation (in ecliptic longitude and obliquity) for a Greenwich date
Calculate	Effects of aberration for ecliptic coordinates
Calculate	RA and Declination values, corrected for atmospheric refraction and geocentric parallax
Calculate	Heliographic coordinates
Calculate	Carrington rotation number
Calculate	Selenographic (lunar) coordinates (sub-Earth and sub-Solar)

The Sun

Type	Description
Calculate	Approximate and precise positions of the Sun
Calculate	Sun's distance and angular size
Calculate	Local sunrise and sunset
Calculate	Morning and evening twilight
Calculate	Equation of time
Calculate	Solar elongation

Planets

Type	Description
Calculate	Approximate and precise position of planet
Calculate	Visual aspects of planet (distance, angular diameter, phase, light time, position angle of bright limb, and apparent magnitude)
Calculate	Position of comet (elliptical and parabolic)
Calculate	Binary star orbit data

The Moon

Type	Description
Calculate	Approximate and precise position of Moon
Calculate	Moon phase and position angle of bright limb
Calculate	Times of new Moon and full Moon
Calculate	Moon's distance, angular diameter, and horizontal parallax
Calculate	Local moonrise and moonset

Eclipses

Type	Description
Calculate	Lunar eclipse occurrence and circumstances
Calculate	Solar eclipse occurrence and circumstances