Only 24 men have ever orbited the moon. And while looking upon the lunar surface must have held a novel appeal for these 24 Apollo astronauts, it is what lay beyond the moon's horizon that was unique:
While in orbit in 1969, a member of the Apollo 10 crew snapped this series of photographs, which we made into the GIF above, that show Earth rising over the lunar horizon.
The Earth is only half visible because of where the moon is in its orbit. If the moon were at its new moon phase, then we would see Earth completely lit.
Apollo 10 was the first of three manned missions to the moon in the year 1969. The three astronauts — Thomas P. Stafford, John W. Young, and Eugene A. Cernan — were on a mission that was described as a "dress rehearsal" for the first moon landing by the following Apollo 11 crew.
Stafford, Young, and Cernan launched atop a Saturn V rocket on May 18, 1969 — just about two months before Apollo 11 launched.
At the time, the Apollo 10 crew had traveled farther from Earth than any human before them. They also got closer to the lunar surface than any Apollo astronaut before them:
The Apollo 10 mission included a version of the lunar lander that Apollo 11 eventually rode down to the lunar surface. Stafford and Cernan detached this lander, called "Snoopy," (shown below) from the command module to test how it performed and to survey the Apollo 11 landing sight in the Sea of Tranquility.
But they did not land the spacecraft on the moon because it was not equipped with enough fuel to get them back to the command module — they would have stranded themselves on the lunar surface if they had landed.
Kipp Teague — who is the director of administrative systems and network services in information technology and resources at Lynchburg College — posted the photos to Flickr in early October, along with over 8,000 additional NASA photos from many of the Apollo missions. His Flickr archive is just part of his larger project "Contact Light," which is a tribute to the space race.