Benjamin Rose
Reputation: 165
Unable to read WCS from SDSS co-added Stripe 82 fits image
I try to read the World Coordinate System (WCS) from a FITS file using satrapy and this code:
from astropy.wcs import WCS
from astropy.io import fits
data = 'file.fits'
hdu = fits.open(data)
w = WCS(hdu[0].header)
I get the error:
WARNING: FITSFixedWarning: RADECSYS= 'ICRS '
RADECSYS is non-standard, use RADESYSa. [astropy.wcs.wcs]
The header file is:
SIMPLE = T
BITPIX = -32
NAXIS = 2
NAXIS1 = 2048
NAXIS2 = 1489
RADECSYS= 'ICRS '
CTYPE1 = 'DEC--TAN'
CTYPE2 = 'RA---TAN'
CUNIT1 = 'deg '
CUNIT2 = 'deg '
CRPIX1 = 1.02500000000000E+03
CRPIX2 = 7.45000000000000E+02
CRVAL1 = 7.34210000000000E-01
CRVAL2 = 2.49604300000000E+01
CD1_1 = 1.09999999400000E-04
CD2_2 = 1.09999999400000E-04
CD1_2 = 0.00000000000000E+00
CD2_1 = 0.00000000000000E+00
COADD_0 = 'fpCs-002570-i5-0112.resamp.fits'
COADD_1 = 'fpCs-002570-i5-0113.resamp.fits'
COADD_2 = 'fpCs-002650-i5-0142.resamp.fits'
COADD_3 = 'fpCs-002650-i5-0143.resamp.fits'
COADD_4 = 'fpCs-002677-i5-0142.resamp.fits'
COADD_5 = 'fpCs-002677-i5-0143.resamp.fits'
COADD_6 = 'fpCs-002700-i5-0032.resamp.fits'
COADD_7 = 'fpCs-002700-i5-0033.resamp.fits'
COADD_8 = 'fpCs-002728-i5-0579.resamp.fits'
COADD_9 = 'fpCs-002728-i5-0580.resamp.fits'
COADD_10= 'fpCs-002738-i5-0084.resamp.fits'
COADD_11= 'fpCs-002738-i5-0085.resamp.fits'
COADD_12= 'fpCs-002820-i5-0032.resamp.fits'
COADD_13= 'fpCs-002820-i5-0033.resamp.fits'
COADD_14= 'fpCs-002855-i5-0038.resamp.fits'
COADD_15= 'fpCs-002855-i5-0039.resamp.fits'
COADD_16= 'fpCs-002873-i5-0075.resamp.fits'
COADD_17= 'fpCs-002873-i5-0076.resamp.fits'
COADD_18= 'fpCs-003362-i5-0033.resamp.fits'
COADD_19= 'fpCs-003362-i5-0034.resamp.fits'
COADD_20= 'fpCs-003362-i5-0035.resamp.fits'
COADD_21= 'fpCs-003384-i5-0535.resamp.fits'
COADD_22= 'fpCs-003384-i5-0536.resamp.fits'
COADD_23= 'fpCs-004128-i5-0289.resamp.fits'
COADD_24= 'fpCs-004128-i5-0290.resamp.fits'
COADD_25= 'fpCs-004157-i5-0042.resamp.fits'
COADD_26= 'fpCs-004157-i5-0043.resamp.fits'
COADD_27= 'fpCs-004198-i5-0528.resamp.fits'
COADD_28= 'fpCs-004198-i5-0529.resamp.fits'
COADD_29= 'fpCs-004207-i5-0538.resamp.fits'
COADD_30= 'fpCs-004207-i5-0539.resamp.fits'
COADD_31= 'fpCs-004868-i5-0374.resamp.fits'
COADD_32= 'fpCs-004868-i5-0375.resamp.fits'
COADD_33= 'fpCs-004874-i5-0587.resamp.fits'
COADD_34= 'fpCs-004874-i5-0588.resamp.fits'
COADD_35= 'fpCs-004895-i5-0202.resamp.fits'
COADD_36= 'fpCs-004895-i5-0203.resamp.fits'
COADD_37= 'fpCs-004905-i5-0168.resamp.fits'
COADD_38= 'fpCs-004905-i5-0169.resamp.fits'
COADD_39= 'fpCs-004933-i5-0529.resamp.fits'
COADD_40= 'fpCs-004933-i5-0530.resamp.fits'
COADD_41= 'fpCs-004948-i5-0109.resamp.fits'
COADD_42= 'fpCs-004948-i5-0110.resamp.fits'
COADD_43= 'fpCs-005566-i5-0395.resamp.fits'
COADD_44= 'fpCs-005566-i5-0396.resamp.fits'
COADD_45= 'fpCs-005603-i5-0614.resamp.fits'
COADD_46= 'fpCs-005603-i5-0615.resamp.fits'
COADD_47= 'fpCs-005633-i5-0582.resamp.fits'
COADD_48= 'fpCs-005633-i5-0583.resamp.fits'
COADD_49= 'fpCs-005642-i5-0242.resamp.fits'
COADD_50= 'fpCs-005642-i5-0243.resamp.fits'
COADD_51= 'fpCs-005658-i5-0069.resamp.fits'
COADD_52= 'fpCs-005658-i5-0070.resamp.fits'
COADD_53= 'fpCs-005765-i5-0161.resamp.fits'
COADD_54= 'fpCs-005765-i5-0162.resamp.fits'
COADD_55= 'fpCs-005770-i5-0548.resamp.fits'
COADD_56= 'fpCs-005770-i5-0549.resamp.fits'
COADD_57= 'fpCs-005777-i5-0013.resamp.fits'
COADD_58= 'fpCs-005777-i5-0014.resamp.fits'
COADD_59= 'fpCs-005781-i5-0546.resamp.fits'
COADD_60= 'fpCs-005781-i5-0547.resamp.fits'
COADD_61= 'fpCs-005792-i5-0587.resamp.fits'
COADD_62= 'fpCs-005792-i5-0588.resamp.fits'
COADD_63= 'fpCs-005792-i5-0589.resamp.fits'
COADD_64= 'fpCs-005800-i5-0568.resamp.fits'
COADD_65= 'fpCs-005800-i5-0569.resamp.fits'
COADD_66= 'fpCs-005813-i5-0605.resamp.fits'
COADD_67= 'fpCs-005813-i5-0606.resamp.fits'
COADD_68= 'fpCs-005823-i5-0572.resamp.fits'
COADD_69= 'fpCs-005823-i5-0573.resamp.fits'
COADD_70= 'fpCs-005898-i5-0610.resamp.fits'
COADD_71= 'fpCs-005898-i5-0611.resamp.fits'
COADD_72= 'fpCs-005918-i5-0587.resamp.fits'
COADD_73= 'fpCs-005918-i5-0588.resamp.fits'
I have compared this to other WCS in header files and it does look different, but I am sure how to fix things. Also I am unsure how to use RADESYSa rather then RADECSYS. There does not seem to be any documentation that I can find. Any help would be appreciated.
Upvotes: 2
Views: 230
Answers (1)
astrofrog
Reputation: 34091
The issue is that the keyword header should be RADESYS not RADECSYS according to the FITS standard (please report this to the people who made this FITS file). To avoid the warning, you can do:
from astropy.wcs import WCS
from astropy.io import fits
data = 'file.fits'
hdu = fits.open(data)
hdu[0].header.rename_keyword('RADECSYS', 'RADESYS')
w = WCS(hdu[0].header)
Upvotes: 4
Related Questions
- Trouble Returning WCS from FITS Image
- FITS with WCS to healpy
- astropy WCS infomation different to header values in fits files
- Plotting SDSS images with python
- Include WCS coordinates in a FITS image
- WCS as matplotlib projection for a data-cube slice loaded using astropy?
- Astropy WCS: "IOError: Header missing END card."
- Getting image from Fits files from SDSS DR10
- Assign WCS coordinates to a FITS image
- Error when using astWCS trying to create WCS object