"Surveys of scientists and amateur astronomers concerning UFOs
In 1973, Peter A. Sturrock conducted a survey among members of the San Francisco chapter of the American Institute of Aeronautics and Astronautics, where 1175 questionnaires were mailed and 423 were returned, and found no consensus concerning the nature and scientific importance of the UFO phenomenon, with views ranging equally from "impossible" to "certain" in reply to the question, "Do UFOs represent a scientifically significant phenomenon?"  In a later larger survey conducted among the members of the American Astronomical Society, where 2611 were questionnaires mailed and 1356 were returned, Sturrock found out that opinions were equally diverse, with 23% replying "certainly", 30% "probably", 27% "possibly", 17% "probably not", and 3% "certainly not", to the question of whether the UFO problem deserves scientific study. Sturrock also asked in the same survey if the surveyee had witnessed any event which they could not have identified and which could have been related to the UFO phenomenon, with around 5% replying affirmatively.
In 1980, a survey of 1800 members of various amateur astronomer associations by Gert Herb and J. Allen Hynek of the Center for UFO Studies (CUFOS) found that 24% responded "yes" to the question, "Have you ever observed an object which resisted your most exhaustive efforts at identification?""
"Hardin suggested “common sense” as the best way to rule out witnesses’ stories that seemed to contain contradictory evidence. Thus, unique or extraordinary details of sightings were not entered into the Blue Book files. As a result, unknowns fell from 60 percent in 1954 to 5.9 percent in 1955 and 0.4 by 1956. Ironically, as the number of unknowns fell, total UFO reports steadily increased."
"Dr. Robert Baker, a former UCLA professor of astronomy and engineering and editor of the Journal of the Astronomical Science, concluded—expressing an opinion that the old Newhouse and Mariana Films were most probably of anomalistic objects. He revealed that the Air Defense Command, (which by then could monitor outer space for a possible Soviet missile attack) had produced “a number of anomalistic alarms.” Dr. Baker commented that he felt this was the only surveillance system that even had a “slight opportunity” of detecting advanced space visitors. Papers from the long time UFO debunker Dr. Donald Menzel as well as five other scientists with less pessimistic views including Stanton Friedman were then read into the record." Project Blue Book 1951-1969