Dr. Yamaoka: Looking at Vickers "CCD Atlas" (pg.174), there are three stars associated with the image of NGC 6239. Two of them are north and west, and faint. The other is east of the core (along our line of sight), and equally as faint. Utilizing a magnitude comparison of the bright star directly north of the galaxy (GSC 3079:41) which is estimated at magnitude 14.2....I would venture to say that your observer has a pretty good chance that his sighting is a bonifide SN suspect....barring any unforeseens! Best, Steve