Apollo 15 was the first of that program's "J missions," which featured longer stays on the lunar surface and more science-heavy timelines. As part of that, for the first time, the lunar module also brought an electric rover to the Moon's surface so astronauts could visit interesting geological features farther away from the landing site.

For the first of these J missions, astronauts David Scott and Jim Irwin landed at the base of the Apennine Mountains, allowing them to explore the Hadley Rille, a deep rift in the Moon’s surface gashed by some early volcanic process. All told, the rover drove a total of 27.9km during the Apollo 15 excursions. But there was only so much the astronauts could do up close. And so it is a good thing, for the first time, they also brought a 500mm telephoto lens to the Moon.

Because weight restrictions were so tight on the mission after inclusion of the 209kg rover, Scott had to argue with mission managers to include the lens, and ultimately they agreed to slightly decrease the spacecraft's abort propellant to gain the extra margin in weight—about one pound.

During four forays onto the lunar surface and during two subsequent days in lunar orbit, Scott took 293 photos with the lens. Because of its zooming capability, the lens allowed for some of the first high-quality photographs to be taken of lunar vistas. For example, Dave Scott's 500mm lens brought out canyon-like geological features in distant ridges that could not be captured with a more standard 60mm lens used with Hasselblad cameras on the Moon.

NASA

RR Auction

RR Auction

RR Auction

RR Auction

RR Auction

NASA

RR Auction

NASA

NASA

NASA

During Apollo 15, the two astronauts had three 70mm Hasselblad camera bodies, in which 70mm refers to the film format. Two of the cameras (one that took black and white photos, one color) had lenses with a 60mm focal length, and the third had a 500mm lens (black and white). The 500mm lens is now being put up for auction by Scott.

In a letter that accompanies the auction, Scott wrote that taking pictures on the Moon was no simple matter: "The camera with the 500mm lens was hand-held and was operated by pressing a single shutter button with automatic film advance. However, without a view finder, a range finder, or a light meter, the astronaut had to point the camera, frame the scene, set the distance, and evaluate the lighting so as to manually set the f-stop, exposure time, and distance. Training for the mission required extensive practice in a spacesuit with pressurized gloves."

Scott said that NASA let him keep the lens after the mission as a memento. In 2012 Congress passed a law clarifying that astronauts in the Mercury, Gemini, and Apollo programs were allowed to sell artifacts they received during those missions. The bill did not apply to lunar rocks, however, nor to missions flown during the space shuttle program and later.

The sale will be conducted by the Boston-based RR Auction, with bidding ending on April 21. The auction house expects the camera lens to sell for between $400,000 and $600,000, said Robert Livingston, the firm's executive vice president. "In private hands I don’t think there’s another 500mm lens," Livingston said. "This has been in Dave’s collection since he came home."

Few items that were actually used on the lunar surface have gone up for private auction, especially of this size and significance to the legacy of Apollo. A cuff checklist worn by Scott during the Apollo 15 mission fetched $364,000 in 2012. The camera lens will be one of the largest lunar surface objects ever auctioned, Livingston said.