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    Re: Sextant with an umbrella
    From: Peter Monta
    Date: 2015 Oct 2, 00:02 -0700



    What's going on in this photo? Is the "umbrella" some sort of prismatic device for backsights?? 


    My guess would have been a sunshade to cut down on stray light into the telescope, but Luc's links make the case for the dipmeter attachment open and shut.

    Two pentaprisms might be a good way to implement it nowadays---a long prism would have to be custom-made, and mirrors could be knocked out of alignment.

    Cheers,
    Peter

       
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