PAL -- A Positional Astronomy Library

astronomy, python, wcs
pip install palpy==1.8.1


PALpy - Python positional astronomy library

PALpy is a python interface to the PAL positional astronomy library (<>). All source code is included with the distribution via git submodules.

To build the python interface from the git repository:

git submodule init
git submodule update
python build
python install

Requires that Cython and numpy are installed.

The interface uses the same names as the C interface with the pal prefix missing:

import palpy as pal

djm = pal.caldj( 1999, 12, 31 )
(r2000, d2000) = pal.fk45z( 1.2, -0.3, 1960 )

All arguments modified by the C API are returned. No arguments are modified. The one routine that is different is palObs which returns a simple dict that can be searched using standard python. The keys to the dict are the short names and the values are another dict with keys name, long, lat and height.

Docstrings are included with each routine describing the python usage and the associated C documentation:

help(palpy) help(palpy.caldj)

See for detailed examples of all functions.


The module provides documentation on how to use the python interface to PAL. It does not contain information on how to use PAL itself.

The basic PAL documentation can be found at

For more information the SLA documentation provides much more detail:

A description paper for PAL was published in the ADASS XXII conference proceedings:

Please consider citing this if you use PAL or palpy in your research.

Further Work

Not all the SLALIB routines are available from PAL. More can be added as need arises.


Copyright (C) 2012, 2014-2016 Tim Jenness ( All Rights Reserved.

This program is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 3 of the License, or (at your option) any later version.

This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.

You should have received a copy of the GNU General Public License along with this program. If not, see <>.