Setup and usage tips is easy to use on Linux, macOS, and Windows. Windows uses Windows Subsytem for Linux for To get star index files, use

Download/install the pre-compiled binary code:

  • Linux / Windows Subsystem for Linux: apt install
  • macOS Homebrew

The major steps in achieving a useful WCS starfield polynomial fit are:

  1. source extraction (identifying star position in image frame)

  2. quad asterism hashing, including tolerance for star position wiggling due to noise.

  3. Match hash to star catalog, at least 3 choices are available:

  4. Bayesian decision process, find extremely high probability solution or reject. tips and techniques

Optional compile: normally not necessary.


apt install libcairo2-dev libnetpbm10-dev netpbm libpng12-dev libjpeg-dev zlib1g-dev swig libcfitsio-dev
curl -O

tar xf*.gz


make py
make extra

make install INSTALL_DIR=~/

Add to ~/.profile

export PATH="$PATH:$HOME/"

do not use ~ to avoid error:

cannot find executable astrometry-engine

Uncomment inparallel in ~/ (or /etc/astrometry.cfg)

Copy the star index files with


If it can’t find the index file, be sure ~/ contains:

add_path /home/username/astrometry/data

~ or $HOME will NOT work!

Reference paper

Program giving azimuth/elevation for each pixel of sky image

Alternative: online image scaling