Package: astrometry-azel
Azimuth/Elevation converter forAstrometry.netNote: If you want to work with the intermediate steps (source extraction) or photometry, see my AstroPy-basedexamples.PrerequisitesAstrometry.net ≥ 0.67or, use theastrometry.net cloud service.Installationpython3-mpipinstall-e.Astrometry.net index filesIf you use astrometry.net on your PC, you may need to install the index
files and setup your config file to point at them:downloadIndex~/dataCommand line optionsPass-through argumentsThe-a--argscommand line option allows passing through a variety of parameters tosolve-field, which underlies this program.
Typesolve-field -horman solve-fieldfor a brief description of the nearly 100 options available.Be sure to enclose the options in quotes.
For example, to specify that the image field is at least 20 degrees in extent:PlateScale~/data/myimg.jpg-a"-L 20"ExamplesCitizen science images often contain extraneous items in the image field of view.
These can very easily breaksolve-field, which is designed for professional science-grade imagery from telescopes and narrow to medium field of view imagers (at least to 50 degree FOV).
To mitigate these issues, judicious use of arguments passed tosolve-fieldvia--argsis probably a good start.The parameters I find most useful for citizen science images include:-L / --scale-low <scale>: lower bound of image scale estimate
-H / --scale-high <scale>: upper bound of image scale estimate
 -d / --depth <number or range>: number of field objects to look at, or range
          of numbers; 1 is the brightest star, so "-d 10" or "-d 1-10" mean look
          at the top ten brightest stars only.For extraneous regions of the image, try making a copy of the original image that has the offending regions cropped out.
If the original image is in a lossy format such as JPEG, consider saving in a lossless format such as PNG after cropping.FITS image inputFITS is a legacy file format commonly used in astronomy.Astrometry.net installed on your PCPlateScaleFITSmyimg.fits-c61.2-149.9-t2013-04-02T12:03:23Z--nc--pnggives NetCDF .nc with az/el ra/dec and PNG plots of the data.
Both files contain the same data, just for your convenience.61.2 -149.9 is your WGS84 coordinates, 2013-04-02T12:03:23Z is UTC time of the picture.wcs.fits from the Astrometry.net WEBSITEfirst rename wcs.fits to myimg.wcs:PlateScaleFITSmyimg.wcs-c61.2-149.9-t2013-04-02T12:03:23Z--nc--pngJPG image inputJPG is commonly used by prosumer cameras.
It's preferable to use lossless formats for scientific imaging such as JPEG2000 or newer file formats.Notes2MASSindexTychoindexways touse astrometry.netastrometry.netsource code releasesastrometry.netGitHubarticleon good robustness of Astrometry.net to shaky, streaked images.build astrometry.netWe use Linux or Windows Subsystem for Linux as follows:wgethttp://astrometry.net/downloads/astrometry.net-latest.tar.gztar xf astrometry.net-latest.tar.gz
cd astrometry*
apt install gcc make libcairo2-dev libnetpbm10-dev netpbm libpng-dev libjpeg-dev python3-numpy python3-pyfits python3-dev zlib1g-dev libbz2-dev swig libcfitsio-dev
make -j
make py -j
make extra -j
make install -j INSTALL_DIR=$HOME/.local/astrometryadd to ~/.bashrc:export PATH=$PATH:$HOME/.local/astrometry/binopen a new terminal to use.Download index filesYou will get various weird errors without the necessary star index files.pythondownloadIndex.py-sourcehttp://broiler.astrometry.net/~dstn/4100/-i820Then, edit ~/.local/astrometry/etc/astrometry.cfg, making the following changes:uncommentinparallelbe sureadd_pathpoints to /home/username/astrometry-data, where username is your Linux username. Don't use ~ or $HOME.optionally, setminwidthsmaller than the smallest FOV (in degrees) you'd ever see. For example, if NOT using a telescope, perhaps minwidth 1 or something.