San Diego, CaliforniaJuly 1955

On July 31, 1955, a 17-year-old student in San Diego, California, used binoculars to watch an unusual object in the night sky for about 20 minutes. The object appeared round, glowed blue, and changed to yellow as he watched. At first he saw one large object, but then two smaller objects seemed to rotate around the larger one. The object remained stationary in the northeast, high above the horizon.

The Air Force investigator noted that the observer was young and may have lacked experience in reporting such sightings. The investigator suggested that the blue and yellow colors might have been caused by light passing through the binoculars, and that any small movement of the binoculars could have made the object appear to move. The fact that the object did not actually change position during the observation, the investigator wrote, supported the possibility that the observer had simply been looking at a bright star.

The weather that night was clear with scattered high clouds. The Air Force checked whether any major stars or planets were visible in that part of the sky and found that Capella, a bright star, was located about 10 degrees above the horizon in the northeast, roughly where the observer had been looking.

In the end, the Air Force concluded the sighting was probably a balloon, though the file notes there was insufficient data for a firm evaluation. The full case file is reproduced below as held by the National Archives, spanning 8 pages.