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    Re: DIY Davis prism directly on the mirror?
    From: Brad Morris
    Date: 2018 Nov 7, 17:08 -0500

    I'm not sure why you would want to glue a prism to your horizon mirror.  Perhaps you could tell us why?

    Further, we don't know the orientation of your prism on the horizon mirror.  Perhaps you could include a sketch.

    If your purpose is to define the vertical, then a one time gluing event is going to make management of the adjustment required rather difficult.  In fact, if you glue the prism down slightly wrong, then you will think the sextant vertical, when it is not.  This will yield a systemic error in observations.  But being unsure of your purpose, this paragraph may be completely off target 


    On Wed, Nov 7, 2018, 3:35 PM Tony Oz <NoReply_TonyOz@fer3.com wrote:


    I'm restoring a Soviet clone of C&P sextant (from mid-sixties).

    I have an idea of glueing a ~6° (as was suggested by the inventor) prism directly on the horizon mirror. I think of doing it on the outer side of the mirror (on the other side from a clamp-spring), and the width of the prism would be approximatelly 1/3 of the transparent half. Of course the prism should be glued as parallel to the transparen|reflective boundary as technically possible. A friend of mine has an UV-hardening glue for glass - completely transparent when set.

    Are there any objections to doing that?

    Please comment.



    60°N 30°E

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