This is why visual sightings of UFOs are the least reliable. The unaided human eye can be tricked to the point of hallucination. A bright light, such as the planet Venus, often appears to move, though a clamped telescope or a sighting bar shows it to be fixed. A visual impression of distance is also unreliable because it is based on an assumed size. Reflections from windows or eyeglasses may provide superimposed views.
Optical defects can turn point sources of light into apparently saucer-shaped objects.
Such optical illusions coupled with a desire to interpret visual images account for many UFO reports. Radar sightings, while more reliable in certain respects, do not provide the information necessary to discriminate between physical objects and such natural phenomena as meteor trails, tracks of ionized gas, rain, or thermal discontinuities. The reliability of such reports depends heavily on whether there were two or more independent witnesses present. This information is provided as a public service, but we cannot guarantee that the information is current or accurate. Readers should verify the information before acting on it.