An article in Popular Science from 1953 urges citizens to take pictures of flying saucers to help the Air Force study them! Oh, but they don't want just any old photographs. Included are instructions for rigging your camera with a diffraction grater grating. This enables experts to determine the kind of light source your photograph captures.

Of course, if the Air Force discovers that your negative indicates the existence of an element not found on this planet, you and your camera will go down in history.

Apparently, that hasn't yet happened. Link -Thanks, David Duncan!