ANY Ideas what this 10 inch Objective is from ....???
Hello All,
I hope everyone's happy and well.
I'd like to ask if anyone recognises what appears to be a large objective cell from possibly a 10 inch refractor telescope which includes collimation adjustment screws, possibly military,industrial or aerial photography ???. The design and finish looks like 1960s to perhaps 1980s. There is a suggestion of faint purple multicoating so perhaps post 1970s/80s. The glass lens is Plano convex (doublet unsure???) of unknown type and is 260mm in diameter and reasonably heavy - 8kg.
Has anyone seen one of these before or know what it is, or might be from?
Thanks in advance for your thoughts and suggestions.
Best
JA
Last edited by JA; 08-05-2018 at 02:50 AM.
Reason: add image
The reflections suggest it’s a singlet lens and the curvuature indicates quite a short focal length so for that aperture it’s not for forming a quality image.
Secondly the three screws have gears and the steep itch of the threads suggests they are for adjusting focus, not collimation - probably all three driven by a ring gear around the outside.
I’d guess it’s either a condenser lens, or a projector lens, possibly from:
A) spotlight used for illuminating actors on stage;
B) large overhead projector, of the kind used for displaying transparencies for lectures.
The latter were common in lecture theatres in the 70s and early 80s, and superseded by computer projectors and now large screens...
I remember seeing something like this in Sky and Telescope many years ago. In that instance, the lens had been used for aerial photography and was converted into a rich-field telescope.
The reflections suggest it’s a singlet lens and the curvuature indicates quite a short focal length so for that aperture it’s not for forming a quality image.
Secondly the three screws have gears and the steep itch of the threads suggests they are for adjusting focus, not collimation - probably all three driven by a ring gear around the outside.
I’d guess it’s either a condenser lens, or a projector lens, possibly from:
A) spotlight used for illuminating actors on stage;
B) large overhead projector, of the kind used for displaying transparencies for lectures.
The latter were common in lecture theatres in the 70s and early 80s, and superseded by computer projectors and now large screens...
Hey Wavy,
Or should I call you Sherlock, lol. What a fascinating insight into the possible origins of this lens. You obviously 'see' waaaay more than I do
Thanks so much for your thoughts guys: Lewis, Bojan, WavyT, TropoB and PCH .... I'll take them on-board for another google images type search to include the objects you've also suggested. I would love to have an ah-ha moment and find an image of the lens used in some sort of optical contraption.
It's an interesting object which I'd like to acquire from overseas and all I have is the overall lens diameter, some 260mm. Dimensioning rather crudely from some of the images to estimate the lens curvature and also guesstimates of curvature from the owner, it's possible to conclude that the focal length is somewhere in the 450 to 1100mm range, most likely 700.
Any further suggestions as to what this might be or is from, would be most appreciated.
One more comment: The faint purple AR coating is most likely single layer magnesium fluoride on Crown glass.
Interesting that there seems to be a bellows arrangement attached to the cell to allow multiple degrees of freedom for collimation/focusing.
Just as a guess I think this might be the objective from a Wild RC10 aerial camera used for mapping photography.
Thanks Paul for your suggestion. I looked on line at some images and was excited when I saw the general size and shape of the Wild RC10, but unfortunately later saw the underside and the objective of the RC10 which was much smaller and arranged differently.... Oh well. Thx
I've now landed the Objective in Australia. It's even larger than first thought. It's nearly 11 inches (270mm odd) in diameter and seems like a well made optic with an AR coat. A rough check of focal length puts it at 850mm. With a few more bits maybe one could make a giant afocal teleside adapter for a large scope or telephoto lens or ...... ???
Looking at a few old B/W movies back in the theatre days I noticed they used large air cooled spotlights which were manually steered and focused to the stage...maybe??
Looking at a few old B/W movies back in the theatre days I noticed they used large air cooled spotlights which were manually steered and focused to the stage...maybe??
Thanks Astro, I did think of that (even small lighthouse type lamp) but in both of those cases tended away from these as many of the theatre lights I researched used fresnel lenses or no lenses although never say never! Alsothere are too many better features for such a use: anti reflective coating, precision grinding of lens, rather than just Using a Moulded only lens, precisely machined aluminium casting and lavish lens support, stainless steel adjustments, what seem to be copper bellows for sealing, and adjustment support.
It will definetly be interesting to find some probably 1970s or 1980s photo of some strange optical contraption of which this is a part and even though it seems too well made and optically ground for such a purpose, your (&Wavytone's) suggestion of a theatrical or perhaps even other type of spotlight is still a possibility. Although I'd discounted the typical theatre lamp (used for fixed illumination), some of the highend followspot type of lamp sometimes uses conventional (non-fresnel) lenses so that might be a possibilty. Thanks and
We were on the right track with many of the suggestions:
1. It was used for aerial and satellite based photography
2. It was used in a military application.
3. It's only part of a larger device /Lens
4. The 3 gears are driven by a ring gear.
It is a lens element from a Perkin-Elmer Type I Aerial Camera 36inch (916mm) f/4.0 ... Kudos to Spectral Joe on CN.
Further internet searching reveals:
It is part of a Perkin-Elmer 36inch focal length (916mm in the new money) f/4 aerial surveillance camera lens. Some history indicates that these were used on various US surevillance/spy aircraft: A-12, SR-71 and possibly also the U2 aircraft and on satellite. They recorded an image on to 9 x 18 inch film. The entire lens assembly weighs in at 200 pounds. The lens I have is 18 pounds of that.
Should be good for some sort of project. Historic pic attached.
.... I'll take them on-board for another google images type search to include the objects you've also suggested. I would love to have an ah-ha moment and find an image of the lens used in some sort of optical contraption. 
