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  1. #1

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    aerial lens modification?

    I acquired a aerial camera lens with the following data Maker: Pacific Optical 12 in f3.8, EFL of 303mm,and a FD of 10.328 in
    It has two elements which are separated by the original mounting distance-- 112mm.
    Now my question is what would happen to these parameters if I increased or decreased the spacing between the two sets of elements.
    They are very heavy and naturally I didn't think of changing anything until they were mounted. I checked around the internet but nothing came out.
    I would like to use it as a camera lens ,but a telescope objective would be a good second choice

    Thanks
    rob

  2. #2

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    Rob, if you change the cell spacing you'll change the focal length and undo all the work Pacific Optical's designers did to make the lens produce good image quality.

    My USAF data sheets list three different 12"/3.8 Pacific Optical lenses, two designed to cover 6x6 and one for 9" x 9". None has dimensions that match yours perfectly. My data sheets are incomplete so there may well have been more 12"/3.8 designs from Pacific Optical.

    Lenses from aerial cameras are often poisoned gifts. Most are hard to put to use, some aren't very useful for general photography.

  3. #3

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    so it's basically a 15 pound paperweight.--well it goes like that sometimes. but it does LOOK impressive.
    thanks for helping out
    rob

  4. #4
    BentleyR's Avatar
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    It would make a nice rich-field astro camera if you mated to a large format CCD or film. I made such a thing from a 7" Aero Ektar and a 4X5 back and got some cool images. If you ever want to get rid of this large paperweight I could offer an inexpensive disposal service.

    Allan

  5. #5

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    Quote Originally Posted by R Paul View Post
    so it's basically a 15 pound paperweight.--well it goes like that sometimes. but it does LOOK impressive.
    thanks for helping out
    rob
    For most but not for all.

    Some years ago one of my friends (?) gave me a doorstop, in the form of the cells from a 36"/8 Bell & Howell telephoto mounted in a light-tight collar the right length. The glass was horrible; scratched, filthy, a little fungus here and there. After I tired of stubbing toes on it I offered it for the cost of shipping on the LF forum. The person who asked for it said he'd use it wide open for shooting wet plate. After it landed on his porch told me he was delighted to have it.

  6. #6

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    I was thinking of doing either of those things with this lens, but just the sheer weight makes working with it difficult. You definitely can't use foamcore for this one.
    I might just get some thin plywood, make a box with the lens at one end and a screen at the other to see what I can get coverage-wise, and borrow a telescope eyepiece to check it out that way. It must be good for something--I just have to find out what that something is.

    Allan ,how fast were the exposures with your camera--did you have to track the camera,or were they short enough not to matter?
    rob

  7. #7
    BentleyR's Avatar
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    I had a tracking mount. Exposures around 15min were good though this was in NYC so the sky was a tad bright! Used Tri-X and did some experiments with Litho film. It turns out that emulsion speed isn't that important for astrophotography. Low reciprocity failure and high contrast are the most important characteristics. If you have a very high contrast emulsion and expose enough that the sky background gets you up past the toe of the curve you get the highest detective quantum efficiency. The litho experiments were interesting - developed under the safelight you'd see an amazing stellar image appear and then, in a few seconds, the whole film went black. Needed to slow the development down.

    The high contrast, slow emulsion approach was used extensively by astronomers before silver halide plates were replaced by CCDs. I was a practicing astronomer in the '80's and Kodak IIIa plates were the king. We'd expose to get the sky up to a density of about 1.0. In a dark place like Chile that would take about 75min at the f/2.7 prime focus of the 4m telescope. if you're interested I recently scanned one of the plates and put on my facebook page (https://www.facebook.com/allan.wirth).

    Good luck with your lens!

    Allan

  8. #8

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    Sorry I don't have a Facebook page (relic that I am). It sounds like one of those activities that gets more and more interesting as you go along with it, but I'm across the river from NYC so I would be limited. But just Orion and the Pleiades were(are) beautiful . I'm afraid you have started me thinking about this.

    thanks for the advice
    rob



 

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