[task #16282] Include ICRS equatorial coordinate type

[Mohammad Akhlaghi]

URL:
  <https://savannah.gnu.org/task/?16282>

                 Summary: Include ICRS equatorial coordinate type
                 Project: GNU Astronomy Utilities
               Submitter: makhlaghi
               Submitted: Mon 24 Oct 2022 06:27:49 PM BST
         Should Start On: Mon 24 Oct 2022 12:00:00 AM BST
   Should be Finished on: Mon 24 Oct 2022 12:00:00 AM BST
                Category: Libraries
                Priority: 5 - Normal
              Item Group: Enhancement
                  Status: None
                 Privacy: Public
        Percent Complete: 0%
             Assigned to: None
             Open/Closed: Open
         Discussion Lock: Any
                  Effort: 0.00


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Follow-up Comments:


-------------------------------------------------------
Date: Mon 24 Oct 2022 06:27:49 PM BST By: Mohammad Akhlaghi <makhlaghi>
As of Gnuastro 0.19, we still don't recognize the "International Celestial
Reference System" or ICRS <https://aa.usno.navy.mil/faq/ICRS_doc> (which is
the IAU approved coordinate system; unlike FK5; that we do support!). 

This stems from the fact that in lib/wcs.c
<https://git.savannah.gnu.org/cgit/gnuastro.git/tree/lib/wcs.c#n758> we have
used NED for the conversion of coordinate system information and NED doesn't
have ICRS!

We should find the conversions (possibly from the link above, or other places)
and implement them in the WCS library because many surveys like SDSS, J-PLUS
or J-PAS use this equatorial coordinate system.

You can reproduce the problem like below:


$ sdssurl=https://dr12.sdss.org/sas/dr12/boss/photoObj/frames
$ wget $sdssurl/301/3716/6/frame-r-003716-6-0117.fits.bz2 -Or.fits.bz2
$ bunzip2 r.fits.bz2 
$ astfits r.fits -h0 --wcscoordsys=eq-j2000
astfits: gal_wcs_coordsys_identify: the 'ICRS' value for 'RADESYS' is not yet
implemented! Please contact us at bug-gnuastro@gnu.org to implement it








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