GDL setup with Astronomy library (open-source IDL replacement)

  1. install GDL

     apt install gnudatalanguage
  2. add to ~/.bashrc
    export GDL_STARTUP=~/.gdl/
  3. Download IDL Astronomy Library and extract

    mkdir -p ~/IDLtoolbox/astrolib
    tar xf astron.dir.tar.gz -C ~/IDLtoolbox/astrolib
  4. create~/.gdl/


    which keeps the current paths and adds all the Astronomy library subdirectories.

Check Astrolib installation

  1. reopen Terminal

  2. In GDL:


    and IDLtoolbox directories should be listed.

IDL / GDL Astrolib vs. Python AstroPy

The comparison is with my Astropy-based coordinate conversion library.


hor2eq, ten(37,54,41), ten(264,55,06), 2466879.7083333d, ra, dec,  /verb, obs='kpno', pres=781.0, temp=273.0


python pymap3d/

revealing less than 2% difference

Example: GDL GNUDataLanguage reading .fits

  1. Download NASA example FITS file and extract

     tar xf
  2. from gdl

     FITS_READ, '', data, header

    showing an image from Hubble Space Telescope.

  3. show FITS headers


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