Setup Astrometry.net and usage tips

Astrometry.net is easy to use on Linux, macOS, and Windows Subsystem for Linux. To get star index files, use our AstrometryGeomap Python package.

python -m astrometry_azel.download

Use the solve-field --index-dir option to refer to the path where the data files are stored.

Alternatively there is an online astrometry.net tool.

Download/install the pre-compiled binary code:

• Linux / Windows Subsystem for Linux: apt install astrometry.net
• 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:

   • USNO-B
   • Tycho-2
   • 2MASS (infrared)

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

Astrometry.new tips and techniques

Optional compile: normally not necessary.

Prereqs:

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

curl -O https://astrometry.net/downloads/astrometry.net-latest.tar.gz

tar xf astrometry.net-*.gz

cd astrometry.net-*

make
make py
make extra

make install INSTALL_DIR=~/astrometry.net

Reference paper