docs: def crval(self):
          """
          Get the world coordinate of the reference pixel.
  
          @rtype: float, float
          """
          try:
              return self.wcs.crval1, self.wcs.crval2
          except Exception as ex:
              logging.debug("Couldn't get CRVAL from WCS: {}".format(ex))
              logging.debug("Trying RA/DEC values")
  
          try:
              return (float(self['RA-DEG']),
                      float(self['DEC-DEG']))
          except KeyError as ke:
              KeyError("Can't build CRVAL1/2 missing keyword: {}".format(ke.args[0]))