Biogon 60mm f/5.6 (NASA Data Camera / MK70)

The 60mm f/5.6 Biogon exists because NASA wanted to measure the Moon. From Apollo 11 the lunar-surface camera was a 500EL rebuilt as the Data Camera — silver-finished for thermal stability, with a glass réseau plate close to the film plane engraved with crosses 10 mm apart “and accurately calibrated to a tolerance of 0.002 mm”, so that film shrinkage and residual distortion could be taken out of the picture in the measuring room. NASA’s own Apollo 11 Hasselblad page says the camera was “fitted with a new Zeiss lens, a Biogon f-5.6/60 mm, specially designed for NASA, which later became available commercially”, and that “careful calibration tests were performed with the lens fitted in the camera in order to ensure high-quality, low-distortion images” — lens and body calibrated as one instrument, not as a lens that happens to be mounted. Zeiss’s own fiftieth-anniversary page names the same combination on Apollo 11.

Why a Biogon rather than a Distagon is the whole point. Bertele’s design is a double-ended reversed telephoto — a compact positive core with large negative menisci at each end, near enough symmetrical — and symmetry is what suppresses distortion, which is the one aberration a photogrammetric lens cannot tolerate. Zeiss had already proved the type at 38mm on the Superwide and, before that, in the Wild Aviogon aerial mapping lens of 1950. The 60 is the same idea at a focal length that covers the 55×55 mm frame comfortably rather than at the extreme.

The price is that the lens does not fit an ordinary camera. Its rear group reaches through the bayonet into the space a mirror would occupy, so it can be mounted only on a Data Camera body or on the MK70, the civilian metric camera Hasselblad Engineering AB built from the 500EL/M — the commercial availability NASA’s page mentions. Hasselblad’s own lens guide is blunt about the restriction, listing the 60mm f/5.6 MK Biogon and the 100mm f/3.5 MK Planar as being “for the MK70 photogrammetric camera only” and noting that a special body was needed for both. Zeiss’s data sheet (Cat. No. 10 48 00) says the same from the optical side: the lens is for réseau cameras — the 500EL Data Camera and the MK70 — and specifies the 4 mm réseau plate with its 25 crosses as part of the system rather than as an accessory. The sheet gives an exact focal length of 61.1 mm, about 740 g, closest focus 0.9 m and Series 63 filters.

The element count is the one specification that cannot be settled here. The Zeiss sheet prints its cross-section as a silhouette and no count beside it; the outline reads as the eight-element, five-group arrangement of the Bertele Biogons, and the schematic drawn for this page follows that pattern, but no consulted source states a figure and sources that quote one disagree. That absence is worth taking seriously for a lens whose whole purpose was metric precision: the numbers Zeiss chose to publish are the ones a surveyor needs, and the optical prescription is not among them.

Open: the element and group count; how many lenses were made in either form, which no source gives; whether the flown lenses differ from the MK lenses in anything but calibration; whether every Apollo landing mission carried this lens or only some; what shutter the barrel holds, which no consulted source names; and whether Nordin’s compendia or Hasselblad Engineering AB’s own literature carry a table for the MK optics. The Club Hasselblad museum pages on the NASA MK 70 refused an automated fetch and remain unread.