[AstroPy] Need some help with wcs
Tue Jan 29 14:49:49 CST 2013
I'm new to astropy but as I see the potential, I like to use it my Ph.d thesis.
After I had fun with some of the tuts and their data I started out to use some of my own data and ran into some problems with wcs.
After I opend up a fits with pyfits.open I tried to use wcs= pywcs.WCS(hdulist.header) to get the wcs data. I got the error mesg: 312 # The header may have SIP or distortions, but no core
313 # WCS. That isn't an error -- we want a "default"
A typical header of the images I want to work with looks like this:
SIMPLE = T / Fits standard
BITPIX = -32 / Bits per pixel
NAXIS = 2 / Number of axes
NAXIS1 = 1023 / Axis length
NAXIS2 = 1023 / Axis length
ORIGIN = 'NOAO-IRAF FITS Image Kernel July 1999' / FITS file originator
EXTEND = F / File may contain extensions
DATE = '2000-08-24T17:53:06' / Date FITS file was generated
IRAF-TLM= '18:52:47 (24/08/2000)' / Time of last modification
TIMESYS = 'UTC ' / P0S| time scale specification
RADESYS = 'FK5 ' / P2S| WCS for this file
EQUINOX = 2.000000E+03 / P0R| equinox
OBSERVER= 'Reiprich / Englhauser' / P0R| observer(s)
TELESCOP= 'Skinakas 1.3m' / P0R| telescope
INSTRUME= 'CH 360 ' / P0R| instrument name
OBS_MODE= 'DIRECT MODE' / RDF| observing mode
FILTER = 'R ' / RDF| filter ID
OBJECT = 'R1825.3+30' / P0R| name of object
DATE-OBS= '2000-06-07T23:54:40' / P0R| time of obs start (UTC)
EXPOSURE= 3.000000E+02 / JER| exposure time (s)
DATE_CCD= '2000-06-08T00:00:20' / JER| end of CCD readout (UTC)
AIRMASS1= '1.005 ' / JER| air mass at obs start
AIRMASS2= '1.007 ' / JER| air mass at obs end
BLANK = 65535 / P0R| undefined integer values
CTYPE1 = 'RA---TAN' / P0R| (assumed) axis type for dim 1
CTYPE2 = 'DEC--TAN' / P0R| (assumed) axis type for dim 2
CRPIX1 = 511.5 / P0R| 'pixel 1 from 0.5 to 1.5' convention
CRPIX2 = 5.125000E+02 / P0R| 'pixel 1 from 0.5 to 1.5' convention
CRVAL1 = 2.763750E+02 / P0R| (assumed) sky coord of 1st axis (deg)
CRVAL2 = 3.045000E+01 / P0R| (assumed) sky coord of 2nd axis (deg)
CDELT1 = -1.3944444444E-04 / P0R| (assumed) X degrees per pixel
CDELT2 = 1.3944444444E-04 / P0R| (assumed) Y degrees per pixel
OBSGROUP= '07JUN00 ' / JER| group ID of observations
OBSFNAME= 'DATA0134' / JER| file ID of observation
HISTORY Changes by FIXQSRC:
HISTORY * add new keywords (everything except for SIMPLE,BITPIX,NAXIS.);
HISTORY filled by information from the observation log files
HISTORY * fix I2 bug of PMIS (negative pixel values)
COMMENT Keyword types:
COMMENT * P0R - reserved in Paper 0
COMMENT * P0S - suggested in Paper 0
COMMENT * P2S - suggested in Paper 2
COMMENT * RDF - present in ROSAT RDF FITS files
COMMENT * JER - introduced by JER
COMMENT * Paper 0: NOST 100-2.0, FITS Definition, http://fits.gsfc.nasa.gov/
COMMENT * Paper 2: Paper II in http://fits.gsfc.nasa.gov/documents.html#WCS
WCSDIM = 2
CD1_1 = -1.3944444444000E-4
CD2_2 = 1.39444444440000E-4
LTM1_1 = 1.
LTM2_2 = 1.
WAT1_001= 'wtype=tan axtype=ra'
WAT2_001= 'wtype=tan axtype=dec'
ZEROCOR = 'Aug 21 19:55 Zero level correction image is Zerom'
CCDSEC = '[1:1024,1:1024]'
CCDPROC = 'Aug 22 1:05 CCD processing done'
FLATCOR = 'Aug 22 1:05 Flat field image is FlatRm with scale=40679.34'
LTV1 = -1.
As it is written in the documantation the values i.e. CRPIX j, PC i j or CD i j, CDELT i,CTYPE i, CRVAL i, or CUNIT i have to be present. As you can see in the middle of the header they exist ok the WCSAXES value ist missing but there is WCSDIM instead.
The error message says something about a 'default'. Do those values have to stand in a particular order at a particular position in the header?
I ran verify() but with no negativ result.
Is there, maybe, an example header to which I can refer to? If so I will write myself a tool to re-write the header of all of those 169 targets I have already in my databank. I would revise my header correcting program which update the header after camera output to get the 'right' header once and for all.
Thanks in advance,
"A little learning never caused anyone's head to explode!"
"Ein wenig Lernen hat noch niemandens Kopf zum Explodieren gebracht!"
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