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    Re: F. Barker & Son Box Sextant
    From: Brad Morris
    Date: 2016 Apr 8, 14:15 -0400

    Hello Sean

    Regarding that double reflected smear.

    Every surface of every lens can contribute that off axis smear.  The slightest fleck of dirt can offset a surface, making the smear appear.

    You must bravely take every single lens and mirror out of the telescope. Clean everly lens, being careful not to leave fingerprints. Clean all banking surfaces.  Replace all lenses.  Ditto the mirrors.  Re-assemble slowly and carefully.

    I've done this for every telescope, for every instrument in my possession.  It's un-nerving at first, but once you gain confidence, you will note that these instruments were designed to be taken apart and reassembled

    Brad

    On Apr 7, 2016 11:30 AM, "Sean C" <NoReply_SeanC@fer3.com> wrote:

    There is something amiss there.....

    -Geoffrey Kolbe

    Yes, but what? I actually just carefully separated the face plate which holds the working parts from the case by removing three tiny screws from the periphery of the case. I could see nothing wrong with either mirror (other than what appered to be some very minor, scattered pitting and a bit of frosting at the edges of the index mirror.) I don't believe there's anything wrong with the telescope since the direct images were not distorted. I even rotated the telescope in its retaining ring while I was looking through it and there was no change in the distortion.

    Before I removed the face plate, I thought maybe the retaining screw for one of the mirrors was too tight, perhaps causing the mirror to bow a little. But upon closer examination out of the case, I saw that the screws are pushing against a retaining clip, which in turn pushes against the edges of the mirror. (See attached drawing.) I didn't dare remove the mirrors from their mounts for fear of damaging them or otherwise screwing something up. So, I'm at a loss as to what could be causing the problem. Any ideas from our resident experts would be greatly appreciated.

    For now, it seems to be in good enough shape to do sun sights, at least.

    Regards,

    Sean C.



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