docs: def ossos_pointings(self):
          """
          plot an OSSOS observation on the OSSOS plot.
          """
          match = re.match('(\d+)\D(\d+)', self.expnum.get())
          if match is not None:
              expnum = int(match.group(1))
              ccd = int(match.group(2))
              x = 2112 / 2.0
              y = 4644 / 2.0
          else:
              expnum = int(str(self.expnum.get()))
              ccd = 22
              x = 1000
              y = 4644 - 15 / 0.185
          header = None
          try:
              header = storage.get_astheader(expnum, ccd=ccd)
          except:
              if header is None:
                  print "Didn't get a header... "
                  return
  
          ossos_wcs = wcs.WCS(header)
          (ra, dec) = ossos_wcs.xy2sky(x, y)
  
          class MyEvent(object):
              def __init__(self, x, y):
                  self.x = x
                  self.y = y
  
          (x, y) = self.p2s((math.radians(ra), math.radians(dec)))
          event = MyEvent(x, y)
          self.create_pointing(event, label_text=header['OBJECT'] + ' ccd{}'.format(ccd))