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[Telescopes] Brashear Refractors

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  • Ed Majden
    I m trying to track down some information on refractor telescopes built by John A. Brashear in the early part of this century, around 1910. Most refractors of
    Message 1 of 3 , Mar 1, 2000
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          I'm trying to track down some information on refractor telescopes built by John A. Brashear in the early part of this century, around 1910.  Most refractors of this period were built with an F-ratio of f-15 or longer to control chromatic aberrations.  Does anyone know if he built any astronomical refractors with  faster F-ratios, say f-10 or so?  A fellow I know claims he has a 5 inch Brashear refractor with a tube length of 57 or so inches.  After looking at the photographs of this instrument, I really think it is a 4 inch clear aperture instrument even if the front element measures 5 inches or so across.  Can anyone shed some light on this?  Brashear made high quality astronomical telescopes so I doubt that he would make an F-10 - 5 inch at the cost of introducing un-wanted colour.
       
      Ed
    • Geoff Gaherty
      ... Although _most_ achromatic refarctors were made with focal ratios of about f/15, not all were. As I mentioned in another thread, I just finished reading
      Message 2 of 3 , Mar 1, 2000
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        epmajden@... writes:
        >Brashear made high quality astronomical telescopes so I doubt that he
        >would make an F-10 - 5 inch at the cost of introducing un-wanted colour.

        Although _most_ achromatic refarctors were made with focal ratios of about
        f/15, not all were. As I mentioned in another thread, I just finished
        reading Starlight Nights, Leslie Peltier's autobiography. In that book he
        describes how he was loaned a 6" refractor dating from the 1890s. He
        worried about how he would be able to fit it into his dome, which was
        designed for a classic 4" f/15. When it arrived, he thought one of the
        boxes must be missing, since they were so small. On opening the boxes, he
        discovered that this telescope was an f/8, apparently specifically built
        for searching for comets; in fact it was _shorter_ than his 4"! It was
        reading about this scope that has led me to obtain a Celestron CR150,
        which has virtually identical specifications to Peltier's scope. Since I
        usually name my scopes, I'm going to name this one Leslie in his honor.

        Geoff Gaherty
        Toronto
      • astralplastics
        Gee, sorry to take seven years to reply to you, Ed. I just stumbled upon your question while doing a Google search. Brashear made refractors in the f/10 and
        Message 3 of 3 , Nov 4, 2007
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          Gee, sorry to take seven years to reply to you, Ed. I just stumbled
          upon your question while doing a Google search.

          Brashear made refractors in the f/10 and f12 ranges as well as f/15.
          The Hastings-Brashear flint forward doublets had excellent color
          correction and I have owned a few f/12's. Remarkably fine color
          correction for that ratio. Barry Greiner at D & G has also commented
          to me about the surprisingly good color in those faster tubes.

          Bart Fried
          oldscope@...


          --- In telescopes@yahoogroups.com, "Ed Majden" <epmajden@...> wrote:
          >
          > I'm trying to track down some information on refractor
          telescopes built by John A. Brashear in the early part of this
          century, around 1910. Most refractors of this period were built with
          an F-ratio of f-15 or longer to control chromatic aberrations. Does
          anyone know if he built any astronomical refractors with faster
          F-ratios, say f-10 or so? A fellow I know claims he has a 5 inch
          Brashear refractor with a tube length of 57 or so inches. After
          looking at the photographs of this instrument, I really think it is a
          4 inch clear aperture instrument even if the front element measures 5
          inches or so across. Can anyone shed some light on this? Brashear
          made high quality astronomical telescopes so I doubt that he would
          make an F-10 - 5 inch at the cost of introducing un-wanted colour.
          >
          > Ed
          >
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