def parse_coordinates(header):
"""Returns a WCS object"""
wcs = WCS()
try:
wcs.crval = header['crval1'], header['crval2']
wcs.crpix = header['crpix1'], header['crpix2']
wcs.cdelt = header['cdelt1'], header['cdelt2']
except KeyError:
logger.warn("Coordinate system not specified in FITS")
raise
try:
wcs.ctype = header['ctype1'], header['ctype2']
except KeyError:
wcs.ctype = 'unknown', 'unknown'
try:
wcs.crota = float(header['crota1']), float(header['crota2'])
except KeyError:
wcs.crota = 0., 0.
try:
wcs.cunit = header['cunit1'], header['cunit2']
except KeyError:
# Blank values default to degrees.
logger.warning("WCS units unknown; using defaults")
wcs.cunit = '', ''
wcs.wcsset()
return wcs
def parse_coordinates(table):
"""Returns a WCS object"""
wcs = WCS()
my_coordinates = table.getkeyword('coords')['direction0']
wcs.crval = my_coordinates['crval']
wcs.crpix = my_coordinates['crpix']
wcs.cdelt = my_coordinates['cdelt']
ctype = ['unknown', 'unknown']
# What about other projections?!
if my_coordinates['projection'] == "SIN":
if my_coordinates['axes'][0] == "Right Ascension":
ctype[0] = "RA---SIN"
if my_coordinates['axes'][1] == "Declination":
ctype[1] = "DEC--SIN"
wcs.ctype = tuple(ctype)
# Rotation, units? We better set a default
wcs.crota = (0., 0.)
wcs.cunit = table.getkeyword('coords')['direction0']['units']
# Update WCS
wcs.wcsset()
return wcs
