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Re: Collimating the dob

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  • pasushkopa
    Hello Max.. I m glad all this came up. I ve looked at the peephole diagram you cited and have a question. What s shown in the diagram is what I see through my
    Message 1 of 10 , Dec 1, 2002
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      Hello Max..

      I'm glad all this came up. I've looked at the peephole diagram you cited and have a question.

      What's shown in the diagram is what I see through my peephole with one exception. The reflection of the main mirror is not centered in the secondary. Everything else within the reflection of the main mirror is all lined up and the secondary is centered in the focuser.

      I haven't had a chance to star test the scope, and was just wondering what adverse effects, if any, this configuration would produce.

      TIA very much,

      Chaske

      --- In skyquest-telescopes@y..., Max Fisher <klaman7@y...> wrote:
      > As for the orion collimating instructions put them in the nearest bin then check out http://www.zebu.uoregon.edu/~mbartels/kolli/kolli.html its a bit technical but the part titled 'The Peephole' (its about 3/4 down the webpage) should make things a lot clearer
    • g2baraff
      ... one exception. The reflection of the main mirror is not centered in the secondary. Everything else within the reflection of the main mirror is all lined up
      Message 2 of 10 , Dec 1, 2002
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        --- In skyquest-telescopes@y..., "pasushkopa" <pasushkopa@y...> wrote:
        > What's shown in the diagram is what I see through my peephole with
        one exception. The reflection of the main mirror is not centered in
        the secondary. Everything else within the reflection of the main
        mirror is all lined up and the secondary is centered in the focuser.
        >
        > I haven't had a chance to star test the scope, and was just
        wondering what adverse effects, if any, this configuration would
        produce.
        >
        > TIA very much,
        >
        > Chaske
        *********

        You SHOULD try to get the reflection of the primary centered in
        the secondary. You will have to adjust the tilt screws on the back
        of the secondary spider to do this. But read some of the suggested
        collimating instructions (even the one from Orion, which is OK for
        THIS step) first.

        What you lose, in your present configuration is, possibly some of
        the light coming from your main mirror (depending on how far off
        center your reflection of the primary seems to be) and also possible
        distortion arising from imperfections at the edge of the secondary.
        (When the image of the primary is centered in the secondary, none of
        the light reaching your E.P. will have come from the very edge of the
        secondary.)

        There has been an AWFUL lot of talk recently on many of the forums
        regarding collimation and how difficult it is to do properly. Read
        any of those threads and notice how often the experienced guys tell
        you NOT to be afraid of the job: you won't screw up anything you
        won't be able to get right again later. Listen to them. It doesn't
        have to be done with brain surgery-like precision, and every step you
        take towards proper collimation will pay off. When you find out that
        the added steps no longer are worth it, you'll know that you are now
        being limited by things like atmospherics and the inherent quality of
        your set up. But RELAX!!

        Gene Baraff
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