Frame Counter and Wrist Mirror
Copyright 2017 by Eric M. Jones. All rights reserved.
With thanks to Charlie Duke, Dave Scott, Jack Schmitt, Daniel Schaiewitz, Ken Glover, Ulli and Martina Lotzmann, and Thomas Schwagmeier.
Last revised 4 September 2017.
Labelled detail from AS17-136-20739 showing the righthand side of Gene Cernan's Hasselblad Camera with the frame counter and gross film indicator labeled. The magazine on Gene's camera is B/134. It contains enough color film for about 160 exposures. Magazines containing black-and-white film can be used for about 180 exposures.
This photo of flown Apollo 17 magazine 139/K was taken at the National Air and Space Museum by Ulli Lotzmann. The frame counter at the lower left is marked with radial lines every fifth frame and with numerical labels every tenth frame. On the Gross Film Indicator immediately above the Frame Counter, each white dot represents about 1/8th of the loaded film. When the magazine is fresh, the white arrow is immediately clockwise from the red marking. When the white arrow is immediately counterclockwise from the red marking, all of the film has been used.
Frame Counter Readings - Apollo 11, 12, 14, 15, 16, 17
Readings of the frame counter could help Houston and the crews keep track of film usage. On the early missions (11, 12, and 14) film usage was planned to ensure that, at any point in an EVA, the crews would have enough film on one or both magazines to complete the planned photography. In the case of Apollo 14, readings may have helped identify changes in location during the EVA-2 traverse.
On the later missions (15, 16, 17) during which mulitple magazines were used during any one EVA, the most important use of frame counter readings was to minimize the chance of reaching the end of a magazine during a Rover traverse.
Reading the frame counter was straight forward if the camera wasn't attached to the chest-mounted Remote Control Unit (RCU) or if the magazine had been removed from the camera. Alternately, the astronauts could read each other's frame counter. Instances of these types are described below. During Apollo 14, it is clear from the audio recordings that Alan Shepard and Ed Mitchell often read their own counters and the question of how they were able to do that is the reason this ALSJ page was compiled.
On Apollo 11 and 12, the LM crews took more than enough film outside to cover planned photography during a particular EVA. Armstrong and Aldrin had one color magazine outside on their one EVA, plus a spare Hasselblad with a color magazine attached ready for use on the cabin floor just inside the hatch in case it was needed. They did not provide a frame count at the end of the EVA, nor did Houston request one. On Apollo 12, during each of the two EVAs, Pete Conrad and Al Bean each had one film magazine loaded on their cameras. After an EVA, they put the cameras and attached magazines into the Equipment Transfer Bag, providing opportunities to read the frame counters. Bean did so for his magazine after EVA-1. About halfway through EVA-2, Bean's camera failed. They took it off his RCU and put the camera with its attached magazine in the Hand Tool Carrier (HTC). Pete then gave Al the CDR camera with attached black-and-white magazine. Once Al had the camera mounted on his RCU, he asked Pete to read the frame counter before they continued on.
On the three J missions - Apollos 15, 16, and 17 - each crew had more than enough film outside on each of their EVAs to cover planned photography. If a magazine was almost out of film or had actually run out, they put a darkslide in the magazine, removed the magazine from the camera, provided a frame count reading, and loaded another magazine and reported its frame count as appropriate. On occasion, particulary during Rover deployment, ALSEP deployment, or when one of the astronauts was using a third Hasselblad equipped with a 500-mm focal-length lens, one or both of the astronauts would take his own camera off his RCU and put it on a Rover seat or some other suitable location. Removal of the camera from the RCU provided an opportunity for reading the frame counter on the magazine. On a few occasions, one of the astronauts would ask his partner to read his frame counter. One such occasion is captured by the LRV TV camera during Apollo 15 at 144:36:08 while Dave Scott and Jim Irwin are working at Station 6 on the lower slopes of Mt. Hadley Delta.
On Apollo 15, neither Scott or Irwin planned to take many photographs during the traverses between geology stations. Consequently, Houston and the astronauts could keep a rough tally of how much film had been used and could change magazines as appropriate when they were off the Rover at a geology stop.
On Apollos 16 and 17, the LMPs planned to document the traverse routes by taking a Hasselblad frame once every fifty meters. Possibly because of the resulting higher rate of film use, Young and Duke and Cernan and Schmitt each wore a wrist mirror on his right forearm to provide a view of the frame counter.
Detail from the JSC high-resolution scan of AS16-108-17744 showing John Young's wrist mirror strapped on his right wrist, just above his thumb. This image is one of two incidental exposures Charlie Duke got while advancing the film on his magazine before inserting a dark slide and replacing the magazine before they leave Station 9.
Images of a hand-written letter of authentication and of the mirrored surface (left) and of the mirror's back (right) from the 1995 auction of Charlie's flown wrist mirror and strap by Heritage Auctions. Twenty-three years after the flight, the once-mirrored surface would need polishing before further use.
In the early 1990s, I asked Charlie what the mirror was used for. He replied "To shine into areas to read checklists and things that were difficult to read for some reason. Like decals and things on experiments that you could get under to read it, so you'd use the mirror so you could look in. And we used it to shine light into a dark area. Just things like that." In 2017, when asked how he and John Young had read their frame counters, he replied "I believe that John and I had a small mirror on a Velcro strap that was velcroed around our right wrist."
Reading the Apollo 14 Frame Counters
The only instances we have been identify of any Apollo astronaut reading his own frame counter while outside the LM all occurred during Apollo 14. After several weeks of discussion by e-mail, Glover, Jones, Lotzmann, and Schwagmeier concluded that, if it was possible to rotate the RCU far enough around an axis emerging from the suit and pointing outward parallel to the axis of the camera lens, then it might be possible for each astronaut to read his own frame counter. Evidence that made this rotation seem possible is the following image provided to the ALSJ by Paul Kashuk.
On the left side of the image we have the back of the RCU with two attachment hooks on the horizontal fitting near the top of the back surface and a longer hook at the bottom center. In mounting the RCU on the suit, the bottom hook is engaged with the suit's upper D-Ring at the center of the astronaut's chest and the upper hooks are engaged with the horizontal bars at the top of the hardware attached to the PLSS shoulder harnesses that secure the PLSS to the upper D-ring. In addition to the shoulder harnesses, the PLSS was also attached to the suit with waist harnesses attached near the bottom of the PLSS on either side and then hooked to the lower D-rings at the front of the suit.
In order to understand how far the RCU would have to be rotated to the left to make the frame counter readable, Ulli and Martina Lotzmann performed an experiment with one of the Hasselblads in their collection. Martina held the Hasselbad at chest height and rotated it until she could read the frame counter. The result was that a rotation of about 45 degrees was required. Ulli has labeled an Apollo 12 photo Alan Bean took of Pete Conrad taking Alan's photo, to illustrate a 45-degree rotation.
Rotating an RCU-mounted Hasselblad to make the Frame Counter readable
Ulli Lotzmann then contacted Dan Schaiewitz who, during Apollo, was a leading engineer in the KSC office of Hamilton Standard, the firm that developed and built the PLSS. The information he provided forms the rest of this section.
Schaiewitz told Lotzmann: "Yes, the camera attached to the RCU could be rotated 45 degrees. The following photos should help clarification. (Specifically), PLSS strap connections to the upper suit D-ring and strap material fabrication allow camera/RCU rotation."
PLSS strap connections to the suit.
RCU connections to the upper D-Ring (labeled '4') and to the PLSS shoulder harnesses (labeled '2').
PLSS 1/6th-g counterbalances being used during LM EVA PrepAndPostProcedures.
Hasselblad with RCU bracket and handle. Schaiewitz told Lotzmann: "When lateral force was applied to the camera handle, it acted as a 'lever arm' to produce the torque required to rotate the Camera/RCU combination. Moment of Force (Torque) = Lateral Force (applied to the camera handle) x Distance (from the center-of-gravity of the glove grip to the RCU upper attachment points. Note that the lower RCU attachment will slide on the upper suit D-Ring to allow the desired rotation."
Righthand side of Hasselblad attached to RCU. To bring the frame counter into view, the handle would have been pulled to the astronaut's right. Schaiewitz told Lotzmann: "On several occasions I was asked if I could rotate the Camera/RCU to read the frame counter and I successfully accomplished that objective."
Attaching Hasselblad to RCU
Starting with Apollo 16, each of the moonwalkers wore a wrist mirror fitted to either the watchband or a dedicated Velcro band. The wrist mirror was used to check EMU (Extravehicular Mobility Unit) fittings prior cabin depressurization and, conceivably could have been used to read the frame counter on a Hasselblad magazine. However, the frame counter was on the righthand side of the magazine, so the mirror could be used for that purpose only if the astronaut wore his Velcro watchband or a dedicated Velcro band for the mirror on his right forearm. In June 2017, when asked about how he read his frame counter, Charlie Duke wrote "I believe that John and I had a small mirror on a Velcro strap that was velcroed around our right wrist." Later in June 2017, I found the following at 168:07:20 in the Apollo 16 House Rock chapter when John and Charlie are about to leave North Ray Crater. Charlie asks John "What's my mag count? My mirror's so dirty, I can't even see."
Labelled detail from AS16-108-17628 showing John Young's watchband secured around his right wrist, with both his watch and wrist mirror attached. See, also, a detail from AS16-108-17744
Detail from AS17-141-21608, showing Gene's watch and watchband on his left arm, above his cuff checklist; and what is almost certainly a Velcro strap on his right arm for his wrist mirror, with the mirror out of sight.
Detail from AS17-140-21386, showing Jack's watch and watchband on his left arm, above his cuff checklist. Jack's watch is on the inner part of his sleeve. His mirror strap is on his right arm, but with the mirror out of sight.
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