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19434Re: Focuser Sag

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  • Timm Bottoni
    Mar 2, 2009
      Hi Greg,

      Is there a way to eliminate a variable and actually measure what you
      think is focuser sag? It may be that it is related to the Vixen
      product. Perhaps it is really an alignment issue that is not visible
      but this is just a guess.

      It seems more likely to me that this might be the direction to look
      since, the 66 and 90 WO scopes have completely different designs,
      focal lengths, focuser designs, etc. If the two products act the
      same, and the are so different, it would lead me think that the
      problem lies somewhere else, since what is the probability that those
      two completely different products would exhibit the exact same problem
      with the Vixen, but not with each other. Maybe through process of
      elimination and careful measuring you can figure out the root cause.

      Hope it helps somehow. Give us more feedback when you can and we
      will try to help while it's still cold out and we are too chicken to
      go outside and freeze our butts off.


      --- 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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