FITS Header comment line

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Rob Morgan

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Sep 17, 2022, 7:21:21 PMSep 17
to astrometry
Where does this fits header line come from?   “--End of Astrometry.net WCS—“ 

I'm using an older dll "cfitsio"  in my program and it seems to stop reading any headers after this line.  My guess is since the line contains the word "End" the library thinks it's finished and stops reading the headers.  Anyway just want to know if there is a simply way to not have this line added to the headers?

Thanks
--Rob

Dustin Lang

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Sep 18, 2022, 8:46:51 AMSep 18
to Rob Morgan, astrometry
It comes from here,

Also note that the END card is added a few lines later.

I'd be pretty surprised if CFITSIO incorrectly stopped reading the header at that point.  A FITS header ends when a header line *starts* with the string "END" (upper case).  The 'listhead" program uses CFITSIO and it can understand those headers fine.

cheers,
dustin



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Rob Morgan

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Sep 22, 2022, 1:15:21 PM (10 days ago) Sep 22
to astrometry
Thank for the info....   I did a bit more digging and found that if I just save the file under PixInsight I can then read the KeyName RA using CFITSIO otherwise it doesn't seem to be part of the header.  Attached is a test file where CFITSIO does not see RA.   I guess PixInsight is reorganizing and adding to the header, but I'm no expert at fits.  I guess WSC does write out RA or Dec KeyNames. 
Boo Uma .fits

Dustin Lang

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Sep 22, 2022, 1:24:31 PM (10 days ago) Sep 22
to Rob Morgan, astrometry
Right, the WCS header doesn't have "RA" or "DEC" header keywords.  It does have CRVAL1 and CRVAL2, which are RA and DEC at the reference pixel (which is given by x = CRPIX1, y = CRPIX2).  If you use solve-field --crpix-center, then the reference pixel is set to be the center pixel, so then CRVAL1 and CRVAL2 are RA,Dec of the field center.

cheers,
dustin


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