[AstroPy] Pywcs not reading transformation matrix correctly

Oliver King ogk@astro.caltech....
Thu Jul 26 12:03:46 CDT 2012


Hi JB,

The WCS does not have a RADECSYS keyword; the CTYPE is TAN-SIP. Here are all the WCS parameters (excluding the polynomial coefficients). This is an image which has had a WCS attached by the astrometry.net software.

CTYPE1  = 'RA---TAN-SIP' / TAN (gnomic) projection + SIP distortions            
CTYPE2  = 'DEC--TAN-SIP' / TAN (gnomic) projection + SIP distortions            
WCSAXES =                    2 / no comment                                     
EQUINOX =               2000.0 / Equatorial coordinates definition (yr)         
LONPOLE =                180.0 / no comment                                     
LATPOLE =                  0.0 / no comment                                     
CRVAL1  =        343.485065456 / RA  of reference point                         
CRVAL2  =        16.1466891384 / DEC of reference point                         
CRPIX1  =        1094.26737976 / X reference pixel                              
CRPIX2  =        1037.56068399 / Y reference pixel                              
CUNIT1  = 'deg     ' / X pixel scale units                                      
CUNIT2  = 'deg     ' / Y pixel scale units                                      
CD1_1   =   -7.75889930453E-05 / Transformation matrix                          
CD1_2   =     4.5042903792E-07 / no comment                                     
CD2_1   =    -3.9690360471E-07 / no comment                                     
CD2_2   =   -7.76314691533E-05 / no comment                                     
IMAGEW  =                 2048 / Image width,  in pixels.                       
IMAGEH  =                 2048 / Image height, in pixels.  

Cheers,
Oliver

On Jul 26, 2012, at 9:58 AM, Jean-Baptiste Marquette wrote:

> 
> Hi Oliver,
> 
>> Is this a known bug? Is there a workaround or do I need to manually edit my FITS file headers?
> 
> What are your CTYPEn and RADECSYS ?
> 
> Cheers
> JB

------
Oliver King
Astronomy Department, Caltech
+1-626-395-4197



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