Well, my original point was that very bright lights will photograph without hard edges, looking sort of blurry, and that the human eye will also not see hard edges on bright lights. The implication being that "UFOs" being photographed would naturally tend to not look very focused.
You pointed out to me that bright lights can actually be photographed with fairly defined edges...so I've been looking around the house at lit lightbulbs, etc, and have found that I actually can see the edges of them pretty clearly...so presumably they could be photographed that way, too.
Meanwhile, I took the dog out for a walk. My street has no street lights, so it's pretty dark out there. I noticed that the outside lights on my neighbors' houses, as well as on my own, when seen from a distance, and in darkness, did in fact appear blurry around the edges to my eye. Perhaps they would not to a camera.
I do assert that a bright light in the night sky, at a considerable distance, would inherently have some blur due to intervening atmosphere...and perhaps also to the contrast between night sky and bright light. Probably most of the time, when the film was developed, the light would be seen as a relatively small dot, which would lose yet more resolution when enlarged.