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19436Re: Focuser Sag

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  • Ed Wozney
    Mar 3, 2009
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      Have you thoroughly examined your mounting of the 66 or 90 on
      the Vixen looking for mount flexure? As you have the same issue with
      the 66 and 90 together to a much, much lesser degree; I'm thinking
      that the difference between the optical axes of the scopes is what is
      behind the varying drift. The difference between the refractors is
      quite small. But between the Vixen and either of the WO scopes is
      substantially greater.

      Just a thought..............

      Forever clear skies & great seeing!
      Cheers, Ed
      RASC - Calgary Centre
      POD Astro Dome Observatory
      N 51° 05' 10.06" W 113° 58' 22.24"

      --- In William-Optics@yahoogroups.com, "Greg" <gbenecke1@...> wrote:
      > I have both a Mergrez 90 and Zenithstar 66 SD that I use both as
      imaging scopes and guide
      > scopes with each other and with a Vixen R200SS Newt. I notice that
      when mated with the
      > R200SS as guide scopes there is an appreciable drift in the guiding
      that I attribute to the WO
      > focusers. The R200SS has a Moonlite focuser on it that is rock
      solid, so any drift I think is
      > from flexure in the focusers of the WO scopes. Interestingly when
      the WO scopes are used
      > with each other the drift is almost nil. I think this is because
      they sag in a similar fashion.
      > Does anyone have any thoughts on how to fight the battle of the
      sag? I have taken apart and
      > tightened and adjusted everything in the focusers and made some
      improvement, but some
      > flex still remains. I have looked at replacing the focusers with
      something like the Moonlite,
      > but one copy would cost as much or more than I paid for the 66.
      > I have been entertaining drilling and tapping holes for set screws
      to lock down the tubes but
      > there goes the resale value if I ever want to sell them. Any
      thoughts are appreciated.
      > Greg
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