What is the hynek scale?

The Hynek scale is a system of classifications created by the astronomer and UFO researcher J. Allen Hynek. There was the 1st kind (visual sightings of unidentifiable flying objects), the 2nd kind (visual sighting and physical evidence), and the 3rd kind (sightings of "occupants" in or around the UFO). there are many extensions of the Hynek scale but this is the base of it.