Tony Lovell and I are bothe members of Peterborough Photographic Society. Back in 2003 we were discussing the possibility of making a super long focus lens ie one in excess of 800mm. focal length. After exploring the Surplus Shed website Surplus Shed we saw some interesting ex govt. optics which seemed to offer some good potential. Tony subsequently bought a surplus flight simulator projector lens - an f3.2 11 inch diameter triplet of 36 inch focal length ie 914mm. I think it cost about £250 which at the time was considerably cheaper than any equivalent camera lens. In fact the only other lenses anywhere near this focal length were/are probably the 800mm Nikkors and Canons and 1000mm Pentax optics ... plus the Leica Apo-Telyt-R modular 280-800mm system which appears to have been discontinued ... and the Leitz Telyt-S 800/6.3 lens discontinued in 1997.
When the lens eventually arrived it weighed approx 20 pounds but there was obviously something not quite right with it. There were some very obvious Newton's rings visible which were indicative of possible balsam separation. However, when Tony took the lens apart he discovered that none of the elements were cemented but strangely, the separate elements were coated in oil. The oil was removed using alcohol and the elements reassembled into the original module.. Here is a picture of one of the 11 inch elements during the cleaning process.
Tony works as a structural engineer and is thus an accomplished CAD designer. This is his initial lens mount drawing designed specifically for use with his Pentax 67 and large format 5 x 4 cameras. Note the attention to very adequate baffling throughout the lens barrel to reduce flare. Also note the very large lens hood to further reduce flare. The lens mount/barrel design parameters were established by trial and error by supporting the original lens module in front of a Pentax 67 camera whilst trying to focus on a distant church tower.
The drawing was submitted to local peterborough engineers MIDAS TECHNOLOGIES (GB) LTD a specialist aluminium fabrication company. This was the result including the natty clips for attaching the lens hood.