A widely circulated photograph from Gemini-7 is incorrectly described as showing two UFOs with 'glowing undersides' (for example, see http://www.geocities.com/Area51/8636/ufoball.jpg).
The actual photograph is part of a pair of views looking
out the co-pilot's (right side) window, at cloud
formations. The nose of the spacecraft is in the field
of view and in this case, sunlight glinting off the white throats of two
nose steering jets caused a flare in the camera, showing
up as a pair of white
glares.
In most "UFO versions" of these images, the boundary between the black nose of the Gemini capsule and the dark Earth below (clearly seen in the original images reproduced here) is subdued and not noticeable, so the location of the glares on the spacecraft's surface is hidden.
Similar views under different lighting conditions, also shown here, confirm that these two thrusters are exactly where the two glares are seen in the photographs in question.
The two photos S-65-63722 and -63723 are the ones presented as 'UFOs', while GT7VIEW1.JPG and GT7VIEW2.JPG are ordinary tourist views included merely for comparison regarding the location of the roll thrusters on the Gemini's nose, as seen out the same window the 'UFO' images were made from.
Here's the second GT7 photo showing the 'glare UFOs'.
Gemini-7 view S-65-63145
Gemini-7 view S-65-63730
Early in the Gemini-4 flight, co-pilot Ed White had taken a few shots of the Titan-2 second stage which the astronauts were trying to rendezvous with. It is visible in the upper right corner of this view. When shown this photo, McDivitt immediately and unambiguously identified it as the upper stage, although it is often presented on the Internet as a UFO. Some analysts suggest that McDivitt's "beer-can-shaped" UFO seen a day later was the same stage under different viewing conditions, but Mcdivitt does not agree.
As can be seen from this view of the Gemini's Titan booster second stage in ground processing, it is indeed "beer can shaped", and may indeed have been the cause of McDivitt's sighting. Clear photographs of the second stage of the Titan-2 were also taken by Gemini-7 astronauts who made a rendezvous maneuver in December 1965. It's probably no coincidence that the only two Gemini missions that carried out rendezvous maneuvers with their booster upper stage -- Gemini-4 and Gemini-7 -- also are famous for "UFO encounters".
Part 2: Here's a lower resolution version of photos of the Saturn third stage which have been published as 'UFOs'.
Part 3: Here is the magazine cover and the Saturn thrid stage together for comparison.