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Thread: Your Oldest Lens

  1. #41

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    Re: Your Oldest Lens

    This is my contribution to the "age game"!

    The maker is Henry Shuttleworth (either junior or senior) of 23 Ludgate Street, London.
    They made the whole range of "Scientific Instruments" between about 1765 and "juniors" death around 1810.

    It is a standard front achromat from one of their telescopes with focal length of 9", F7..The cement (or oil perhaps) needs changing. The glass is very pale green. When I am brave enough to remove from the mount and reglue, I will be using it regularly!
    Attached Thumbnails Attached Thumbnails shuttleworth3.jpg  

  2. #42
    Richard K. Richard K.'s Avatar
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    Re: Your Oldest Lens

    You win...

    And so far I am resisting temptation to look for telescopes....hmmm....is eBay a good source....what are average prices for circa 1800 telescopes?...no...I'm not going there!....maybe ...just a quick look....
    When I was 16 I thought my father the stupidest man in the world; when I reached 21, I was astounded by how much he had learned in just 5 years!

    -appropriated from Mark Twain

  3. #43

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    Re: Your Oldest Lens

    I have waited to present this until I had got my "quota" of 1780-1850 telescopes.
    Before around 1780, the objective was often a single lens. Both crown/flint and flint/crown combinations exist.

    My experiences are:

    - they are all on sale in the UK - at least those without the "antik" atmosphere which starts anything of brass which has a maritime image at over 100. Often from places like Devon, Cornwall, Liverpool.
    - plenty of websites with makers/when active/images of engraving.
    - Lots and lots of forgeries - but mostly of Ross and Dolland. For Ross, these are stamped whilst Dollond has copperplate copies.
    - Difference between the winning bids is condition dependent rather than manufacture.
    Say 200 for a perfect condition for a known/period telescope whilst lens chips/delamination of the objective/lost cladding brings the price down to just 10s of s or less!
    - UK was a favorite market for French telescopes up to Franco-Prussian war (1870) so
    Darlot was not alone. Unnamed means imported. Shops made engravings too.
    - Focal lengths vary from around 9" up to about 20".
    - Dimension of the objective are from 1.25" to 2".
    -Threads are surprisingly good - but the objective lens always seen to be burnished in from the rear.

    I got into this market to collect/repair a series of telescopes for my many grandsons. I have quite a lot of extra achromats which I draw on to replace the usually destroyed objective lens. My experience is that the erector/eyepiece lens (the difficult area) are in perfect condition. But sometimes the objective lens are OK as well!

  4. #44
    Richard K. Richard K.'s Avatar
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    Re: Your Oldest Lens

    Steven, thanks for this fine information!!
    When I was 16 I thought my father the stupidest man in the world; when I reached 21, I was astounded by how much he had learned in just 5 years!

    -appropriated from Mark Twain

  5. #45

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    Re: Your Oldest Lens

    Petzval projection front achromats seem perfect for replacments in telescopes. Which can't surprise as that is where the design came from (telescope optics to photographic optics). RR achromats I have tried work but introduce a little sharp edge chromatic colouring.

  6. #46

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    Re: Your Oldest Lens

    Quote Originally Posted by Steven Tribe View Post
    Petzval projection front achromats seem perfect for replacments in telescopes. Which can't surprise as that is where the design came from (telescope optics to photographic optics).
    Are you sure of this? I've always read that Joseph Petzval designed the lens specifically for the Daguerreotype process, which needed the extra speed.
    "I love my Verito lens, but I always have to sharpen everything in Photoshop..."

  7. #47

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    Re: Your Oldest Lens

    Absolutely sure (almost)!
    There was a complete link between the opticians of the period who were making telescopes at the time and the first lens makers. Chevalier was making lenses for telescopes long before he did them for the early photo experimenters.
    There is an interesting website where a researcher has access to sophisticated optical analyses. He "borrowed" about 30 pre-1820 telescopes from collections around the USA - split them up and did individual studies of the singles lenses and the front achromat. The front objective "achromats" turned out to live up to their description - well almost! I admire Petzval's achievement, but I think he basically accepted the formulation of the well-tried front achromat in his design and then restricted his calcuations to the degrees of freedom available with the double lens pair at the back in order to boost the speed.
    I can find the website link if there is interest?

  8. #48
    funkadelic
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    Re: Your Oldest Lens

    Quote Originally Posted by Steven Tribe View Post
    Absolutely sure (almost)!
    There was a complete link between the opticians of the period who were making telescopes at the time and the first lens makers. Chevalier was making lenses for telescopes long before he did them for the early photo experimenters.
    There is an interesting website where a researcher has access to sophisticated optical analyses. He "borrowed" about 30 pre-1820 telescopes from collections around the USA - split them up and did individual studies of the singles lenses and the front achromat. The front objective "achromats" turned out to live up to their description - well almost! I admire Petzval's achievement, but I think he basically accepted the formulation of the well-tried front achromat in his design and then restricted his calcuations to the degrees of freedom available with the double lens pair at the back in order to boost the speed.
    I can find the website link if there is interest?
    When it comes to lens history, you'll always find interest here.

  9. #49

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    Re: Your Oldest Lens

    You may be absolutely sure, but that doesn't make it so.

    To those who try to downplay what he did, I say again, J. Petzval was the first to mathematically calculate a lens design given the requirements for greater speed and workable photographic requirements. All the lenses before him were slow or had myriad aberrations. They were made by trial and error, and the designs were guesswork.

    He got out his pen and paper, and mathematically created a design that was many times faster, and that design was used for 60 years. He built a prototype and it work as he had calculated. Just because part of his design is a cemented doublet, like almost all lenses before or after, doesn't mean he simply tweaked one or invented something obvious. If it were easy someone else would have taken an F16 single element design and created an F3.8 multi element design.

    Also, the meniscus lenses at the time were reversed, concave side out, weren't they? Petzvals design is convex out. It was a novel, revolutionary, and lasting invention.

  10. #50

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    Re: Your Oldest Lens

    Quote Originally Posted by Richard K. View Post
    I guess this one, a Ross Petzval from 1842/43, is now my oldest. Very sharp (in the center) and amazingly clean glass:



    I even made a pair of stops for it:

    Richard, those are tuit's. Anybody knows that. That reminds me. I need to get a round tuit. My wife told me so.
    He is no fool who gives what he cannot keep..to gain that which he cannot lose. Jim Elliot, 1949

    http://tonopahpictures.0catch.com

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