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Re: Does anybody have one of the "too short" focal reducers?

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  • deepspacenutz
    Sure thing, email me at deepspacenutz@yahoo.com and I ll send it out your way to play with. Maybe you can verify the actual FR... :) ... with it.
    Message 1 of 31 , Aug 31, 2007
      Sure thing, email me at deepspacenutz@... and I'll send it out
      your way to play with. Maybe you can "verify" the actual FR... :)

      --- In LX200GPS@yahoogroups.com, "plalbrecht" <plalbrecht@...> wrote:
      >
      > --- In LX200GPS@yahoogroups.com, "deepspacenutz" <deepspacenutz@>
      > wrote:
      > >
      > > I have one of those little nightmares. I sent it back to Meade for a
      > > "new" one and they sent the same one back so I guess I'm stuck
      with it.
      >
      > If you like, I'd like to take a shot at it. I'll pay you for postage
      > and return it when done. Maybe I can get it to work. Maybe we'll learn
      > something from it, like, it's not so bad after all.
      >
      > I don't expect I'd need it for very long.
      >
      > Regards,
      >
      > Pete
      >
    • plalbrecht
      ... Run through all that again and assume microfocusers were never invented; what do you come up with? (I don t know. I m too lazy, and you re the one with the
      Message 31 of 31 , Sep 20 6:27 PM
        --- In LX200GPS@yahoogroups.com, "Conrad Maloney" <conrad@...> wrote:
        >

        > When the Microfocuser is added with the SCT adaptor fitted, the
        > available Backfocus is reduced to 66.8mm.
        >
        > But the Primary Image for the F6.3 (short FL) needs to be at 96.4 mm
        > behind the SCT thread of the Microfocuser adaptor, and the F6.3 (long
        > FL) needs even greater distance of 131.1 mm if the FR has a FL of
        > about 200 mm.
        >
        > This says to me that there is something seriously wrong, since the
        > LX200GPS (8" any way) cannot be used at its design FL with any of the
        > FR's sold by Meade. They can only be used if the Primary Mirror is
        > moved forward to increase the Backfocus distance.


        Run through all that again and assume microfocusers were never
        invented; what do you come up with? (I don't know. I'm too lazy, and
        you're the one with the data).

        I suspect that even if these things don't come out with a focus
        exactly at that 132.9 mm you state, they'll be a lot closer to it than
        when you toss the microfocuser into the mix.

        I don't believe they changed the curves on the optics when they
        introduced the microfocuser. I suspect (but have no evidence either
        way) that the primary and secondary mirror curves have remained the
        same, from LX200 Classic all the way through the GPS (but maybe, maybe
        not, the R). The microfocuser is an afterthought.

        If you have the means to test these optics, and perhaps have access to
        a Classic, and a GPS, it might be interesting to see what you measure,
        in terms of radii of curvature and optimum spacing / focus position
        for the two models.


        Pete
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