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Re: Secondary Centered??or not??

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  • tropicalband2000
    Thank you Henry and Jack, despite the black zone which will increase the secondary obstruction by a (negligible) factor the overall quality of the images is
    Message 1 of 21 , Aug 1, 2006
      Thank you Henry and Jack,
      despite the black zone which will increase the secondary obstruction
      by a (negligible) factor the overall quality of the images is
      outstanding.
      I've just compared the scope with a brandnew, perfectly collimated and
      cooled 12" top selling truss and despite the 2" gap all the people of
      the star party were impressed by the crisp images of the XT,
      expecially on the Swan and some of the Sagittarius globs.
      Maybe I got a lucky primary.
      Hope will be of interest.
      G.


      --- In skyquest-telescopes@yahoogroups.com, "Jack Kramer"
      <jak.stargate@...> wrote:
      >
      > From: "tropicalband2000" <w.matilda@...>
      > > The secondary itself it's round and centered but when the
      > > collimation is spot on (barlowed laser method)I still have this
      > > blackside on the left (due to the offsetted glue on the secondary
      mirror?)
      >
      > Giampaolo,
      >
      > Based on your drawing, I wouldn't be concerned about the black area.
      If this were a perfect world, you wouldn't see that. But as we've
      discussed before, it appears that some XT secondary mirrors are not
      exactly cut to the correct dimensions. I think that's the situation
      here. The important thing is the quality of the images when you're
      observing.
      >
      > Jack Kramer
      > Lily Lake, Illinois
      > http://home.att.net/~jak.stargate/wsb/index.html
      >
    • Gene Baraff
      ... It s not clear (from the diagram you uploaded) that there will be ANY increase in the secondary obstruction. You showed us the black edge as seen from
      Message 2 of 21 , Aug 1, 2006
        --- In skyquest-telescopes@yahoogroups.com, "tropicalband2000"
        <w.matilda@...> wrote:
        >
        > despite the black zone which will increase the secondary
        > obstruction by a (negligible)
        > ***********
        It's not clear (from the diagram you uploaded) that there will be ANY
        increase in the secondary obstruction. You showed us the black edge
        as seen from the /focusser/. But when you stand in front of the
        scope and look down at the primary, past the spider and secondary, do
        you see any extra obstruction caused by the black rim of plastic? If
        not, then you have no extra obstruction in your light path.

        Gene
      • Galassi
        You are right. There is no extra obstruction from the black edge (tnx!) G.
        Message 3 of 21 , Aug 1, 2006
          You are right. There is no extra obstruction from the black edge (tnx!)
          G.


          Gene Baraff wrote:
          >
          > --- In skyquest-telescopes@yahoogroups.com
          > <mailto:skyquest-telescopes%40yahoogroups.com>, "tropicalband2000"
          > <w.matilda@...> wrote:
          > >
          > > despite the black zone which will increase the secondary
          > > obstruction by a (negligible)
          > > ***********
          > It's not clear (from the diagram you uploaded) that there will be ANY
          > increase in the secondary obstruction. You showed us the black edge
          > as seen from the /focusser/. But when you stand in front of the
          > scope and look down at the primary, past the spider and secondary, do
          > you see any extra obstruction caused by the black rim of plastic? If
          > not, then you have no extra obstruction in your light path.
          >
          > Gene
          >
          >
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