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    Re: Bris Confusion
    From: Alexandre Eremenko
    Date: 2015 Jun 25, 17:59 +0000

    You can find very fine pictures of the original Bris here,
    together with some theory and some observations.
    
    http://www.math.purdue.edu/~eremenko/Navigation/Sextants/Bris/
    
    The Sun ray enters the dark glass.
    Usually I see 4 bright suns and 6-7 dim ones.
    All glass surfaces must be very clean.
    
    Once I carried it on a rope hanging on my neck under the shirt,
    and the sextant became unusable because the surfaces were covered by sweat vapors:-)
    Cleaning the inner surfaces in non-trivial.
    
    I purchased it from Cassens Plath 10 years ago and they told me that this was the last one
    they had.
    
    Alex.
    ________________________________________
    
    From: NavList@fer3.com [NavList@fer3.com] on behalf of Marty Lyons [NoReply_MartyLyons@fer3.com]
    Sent: Thursday, June 25, 2015 12:01 PM
    To: eremenko@math.purdue.edu
    Subject: [NavList] Bris Confusion
    
    I read the archived articles on the Bris, somewhat confusing. Pretty 
    fascinating though, so I made one. I used three glass welding shields, two 
    clear and one #5 shaded, spaced at slightly different angles.
    My questions are:
    1. Is the light supposed to enter the Bris from the top, in the spaces between 
    the glass or through the back of the shade?
    2. I see what I think are a bunch of reflections. I will say, 1 bright, 2 less 
    bright, 4 dimmer yet and on very dim. Is that correct?
    3. So to understand the principle, I sight the horizon and wait until one of 
    the images comes down or up to the horizon and time it?
    4. I then work the sight backwards, using either manual methods or software solutions?
    
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    View and reply to this message:
    http://fer3.com/arc/m2.aspx/Bris-Confusion-MartyLyons-jun-2015-g31891
    
    
    

       
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