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Re: Focuser Travel

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  • Donald Clement
    ... The profile of a focuser with a fixed tube length, i.e. Crayford, is not that of the focuser base, but that of the tube length. If your focuser base has a
    Message 1 of 3 , Apr 1 6:24 AM
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      --- In atm_free@yahoogroups.com, "microboter" <jdavis211@...> wrote:
      >
      > Almost finished with my crayford style focuser. Its a low profile
      > for 1.25" eyepiece. The height of the focuser base is 1" and I am
      > curious about how long of a draw tube I should cut for it. The draw
      > tube will have an OD of 1.5". This will be installed on a 10" f4.5.
      >
      > I was thinking 2 to 2.5" or so, think this will work?

      The profile of a focuser with a fixed tube length, i.e. Crayford, is
      not that of the focuser base, but that of the tube length. If your
      focuser base has a height of 1" and you want 2.5" of travel, then the
      tube must be at least 3.5" long. The profile is then 3.5" even though
      the base may have a "low profile" of 1". Low profile and long travel
      are mutually exclusive with a Crayford type focuser with fixed tube
      length.

      Don Clement
      Running Springs, California
      www.ClementFocuser.com
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