Astronomer Walter Webb's 1951 UFO Sighting:
From NICAP web site

Date: August 3, 1951. Witness: Walter N. Webb, Chief Lecturer on Astronomy, Charles Hayden Planetarium, Boston, Mass., (former member of the Smithsonian Institution Satellite Tracking Program):

"That summer I was a nature counselor at Camp Big Silver, the Toledo (Ohio) Boy's Club camp on the shores of Silver Lake in southern Michigan, three miles south of Pinckney. It was a clear, moonless night. I had been showing two boys various celestial objects through my 3-1/2 inch reflecting telescope and pointing out constellations. The time was about 11 p.m. or midnight. Suddenly I noticed a glowing yellow, or yellowish-red light moving in an undulating path (but on a straight course) over the hills south of Silver Lake. As the object traveled slowly westward in this peculiar manner, the three of us watched in fascination. It was at such a low elevation that its regular wavelike course caused it to dip behind the hills a few times. At first I frankly didn't realize that I might be seeing anything unusual and thought the object was a plane light. But something was disturbing about that flight path and by the time it dawned on me that planes don't fly on wavy paths, the thing was about to vanish for good behind trees in the foreground. I swung the telescope toward the hills, but it was too late.

"I had seen something strange in the sky that I could not explain. No known object I could think of followed a path like that. The remote possibility that the UFO might have been the reflection of a moving ground light from a rippling inversion layer was quickly rejected, An inversion reflection would appear as a hazy spot of light in the sky much reduced in brightness when compared with its original light source. My UFO appeared to be a bright, glowing object moving in a regular wavy pattern. It is impossible for an inversion layer to produce a smooth rhythmic reflection. A turbulent rippling layer of air would be required, and such a condition would not be capable of producing any image at all."