header keyword for wcs???

Young Ho, Bae wrote on Feb 06, 2007

hi,

I have problem of finding wcs solution on fits image.
There are keywords & values in header related with wcs;

WAT0_001= 'system=physical'
WAT1_001= 'wtype=linear'
WAT2_001= 'wtype=linear'

To find wcs solution, keywords 'CTYPE1' and 'CTYPE2' must be inserted into header before find wcs solution, I know.
In almost case, I assign value 'RA---TAN' to keyword 'CTYPE1' and 'DEC--TAN' to keyword 'CTYPE2', then find wcs solution.

But, in this case I mentioned, which value I assign to each keyword, CTYPE1, CTYPE2 ???

Thank you...

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Mike Fitzpatrick wrote on Feb 06, 2007

The WAT keywords are an IRAF convention, and from the look of them it wouldn't appear as if you have a WCS in the image at all (i.e. the 'system=physical' implies only a pixel coordinate system). The CTYPE keywords are only part of a WCS, you also need CRVAL, CRPIX, and sometimes a CD matrix to define the reference value, reference pixel, and scale/rotation matrix respectively. Please post the entire header (e.g. "imhead image.fits long+") if you think there should be a WCS in the image.

The WCSEDIT and WCSRESET tasks can help, if you're running a recent V2.13 release see also the MKCWCS and MKCWWCS tasks in the IMCOORDS package.

Cheers,
-Mike

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Last post on Feb 06, 2007