GDL setup Astronomy library

To setup the IDL/GDL Astronomy library on Linux: install GDL and add to ~/.profile

export GDL_STARTUP=~/.gdl/gdl-startup.pro

Download IDL Astronomy Library](https://idlastro.gsfc.nasa.gov/ftp/astron.tar.gz) and extract

mkdir ~/astrolib

tar xf astron.dir.tar.gz -C ~/astrolib

Create~/.gdl/gdl-startup.pro

!PATH=!PATH+':'+Expand_Path('+~/astrolib/')

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

Check: reopen Terminal and type

gdl

In GDL:

print,!PATH

and ~/astrolib should be included in the printout.

Examples: Astrolib vs. AstroPy

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

  • GDL

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

  • Python shows less than 2% difference.

    python pymap3d/azel2radec.py

reading .fits:

Download NASA example FITS file and extract

tar xf w0bs0102t_c0h.fit.gz

From gdl show an image from Hubble Space Telescope.

FITS_READ, 'w0bs0102t_c0h.fit', data, header

TVSCL,data

Show FITS headers

PRINT,header