docs: def comparison_image_list(self):
          """
          returns a list of possible comparison images for the current cutout.  Will query CADC to create the list when
          first called.
          @rtype: Table
          """
  
          if self._comparison_image_list is not None:
              return self._comparison_image_list
  
          ref_ra = self.reading.ra * units.degree
          ref_dec = self.reading.dec * units.degree
          radius = self.radius is not None and self.radius or config.read('CUTOUTS.SINGLETS.RADIUS') * units.arcminute
          print("Querying CADC for list of possible comparison images at RA: {}, DEC: {}, raidus: {}".format(ref_ra,
                                                                                                             ref_dec,
                                                                                                             radius))
          query_result = storage.cone_search(ref_ra, ref_dec, radius, radius)  # returns an astropy.table.table.Table
          print("Got {} possible images".format(len(query_result)))
          ans = raw_input("Do you want to lookup IQ? (y/n)")
          print("Building table for presentation and selection")
          if ans == "y":
              print("Including getting fwhm which is a bit slow.")
          comparison_image_list = []
          if len(query_result['collectionID']) > 0:  # are there any comparison images even available on that sky?
              index = -1
              for row in query_result:
                  expnum = row['collectionID']
                  if expnum in self._bad_comparison_images:
                      continue
                  date = Time(row['mjdate'], format='mjd').mpc
                  if Time(row['mjdate'], format='mjd') < Time('2013-01-01 00:00:00', format='iso'):
                      continue
                  exptime = row['exptime']
                  if float(exptime) < 250:
                      continue
                  filter_name = row['filter']
                  if 'U' in filter_name:
                      continue
                  if filter_name.lower() in self.hdulist[-1].header['FILTER'].lower():
                      filter_name = "* {:8s}".format(filter_name)
                  fwhm = -1.0
                  if ans == 'y':
                      try:
                          fwhm = "{:5.2f}".format(float(storage.get_fwhm_tag(expnum, 22)))
                      except:
                          pass
                  index += 1
                  comparison_image_list.append([index, expnum, date, exptime, filter_name, fwhm, None])
          self._comparison_image_list = Table(data=numpy.array(comparison_image_list),
                                              names=["ID", "EXPNUM", "DATE-OBS", "EXPTIME", "FILTER", "FWHM", "REFERENCE"])
          return self._comparison_image_list