[AstroPy] WCS solutions from table HDUs
s.r.walker101 at googlemail.com
Fri Nov 27 13:07:29 EST 2015
When I try to read the wcs header from a table HDU, the returned wcs object is not valid (i.e. it maps pixel coordinates to pixel coordinates.)
My understanding is that `astropy.wcs` uses `wcslib` under the hood to handle most of the implementation, and `wcslib` supports table HDUs just fine. An example astrometric solution is given below:
TCTYP3 = 'RA---ZPN' / WCS projection
TCTYP6 = 'DEC--ZPN' / WCS projection
TCRVL3 = 307.241977403642 / RA at reference pixel
TCRVL6 = 25.3168420637255 / Dec at reference pixel
TCRPX3 = 1024.4417725
TCRPX6 = 1023.831605
TC3_3 = -0.00140653080291281
TC6_6 = -0.00140646456957538
TC3_6 = 1.3189450212842E-05
TC6_3 = -1.3038301062367E-05
TV6_1 = 1.
TV6_3 = 9.26153828229481
TV6_5 = -938.934425623138
TV6_7 = 688883.879115836
I’ve seen these keywords mentioned in the Paper I description, and I believe they are valid. The solution creates a valid astrometric solution when using the equivalent image wcs keywords (CD1_1, CRPIX etc.).
If this is not supported I’d be happy to attempt an implementation - I am relatively familiar with `wcslib`. My knowledge of the standard however is a little shaky.
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