Second Example#

Another way of creating a WCS object is via the use of a Python dictionary. This affords us more control over the NAXISn FITS header keyword which is otherwise automatically default to zero as in the case of the First Example shown above.

# Define the astropy.wcs.WCS object using a Python dictionary as input

import astropy.wcs

wcs_dict = {
'CTYPE1': 'WAVE    ', 'CUNIT1': 'Angstrom', 'CDELT1': 0.2, 'CRPIX1': 0, 'CRVAL1': 10, 'NAXIS1': 5,
'CTYPE2': 'HPLT-TAN', 'CUNIT2': 'deg', 'CDELT2': 0.5, 'CRPIX2': 2, 'CRVAL2': 0.5, 'NAXIS2': 4,
'CTYPE3': 'HPLN-TAN', 'CUNIT3': 'deg', 'CDELT3': 0.4, 'CRPIX3': 2, 'CRVAL3': 1, 'NAXIS3': 3}
input_wcs = astropy.wcs.WCS(wcs_dict)