[sr #110941] converting wcs-to-img asttable does not work

[anonymous]

URL:
  <https://savannah.gnu.org/support/?110941>

                 Summary: converting wcs-to-img asttable does not work
                   Group: GNU Astronomy Utilities
               Submitter: None
               Submitted: Sun 08 Oct 2023 11:44:19 AM UTC
                Category: Table
                Priority: 5 - Normal
                Severity: 3 - Normal
              Item Group: Output not reasonable
                  Status: None
                 Privacy: Public
             Assigned to: None
        Originator Email: lesliekipphunt@gmail.com
             Open/Closed: Open
         Discussion Lock: Any
        Operating System: Mac OS


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Follow-up Comments:


-------------------------------------------------------
Date: Sun 08 Oct 2023 11:44:19 AM UTC By: Anonymous
The gnuastro0.15 manual gave the following code (here reproduced the
significant snippet) to convert from CRVALs in RA, DEC to CRPIX in pixels:

for f in $r $g $b; do
       centerpix=$(echo $centerwcs \
                        | asttable -c’arith $1 $2 wcstoimg’ \
                                   --wcsfile=$f-aligned.fits \
                        | awk ’{printf "%g,%g", $1, $2}’)
       astcrop $f-aligned.fits --mode=img --width=$widthpix \
               --center=$centerpix -o$f-use.fits
       rm $f-aligned.fits
done

However, substituting wcstoimg with wcs-to-img does not give the pixel values,
but rather the RA, DEC values in $centerwcs, such that $centerpix is the same
as $centerwcs. 

An analogous formulation is *not* given in the latest (to my knowledge)
gnuastro.pdf for gnuastro-0.20, so it's not clear to me how to revise the
script to obtain the CRPIX values associated with CRVALs for an arbitrary fits
file.

Thanks very much for any enlightenment!








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