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    Re: Sextant with an umbrella
    From: Luc Van den Borre
    Date: 2015 Oct 1, 22:55 +0200

    On 01/10/15 20:32, Frank Reed wrote:
    > What's going on in this photo? Is the "umbrella" some sort of prismatic
    > device for backsights??
    
    Is this one of your quizzes where you already know the answer? :)
    
    I suppose it's a Blish prism to measure dip, by viewing the horizon
    behind next to the horizon in front?
    
    If that's the case this may well be a picture of the man himself with
    his invention... There's a photo of Blish on his Wikipedia page, judge
    yourself:
    https://en.wikipedia.org/wiki/John_Bell_Blish
    
    Patent drawing:
    http://sextantbook.com/2012/04/
    
    Luc
    
    

       
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