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    Re: Can You Bias Ho?
    From: Luc Van den Borre
    Date: 2014 Apr 04, 09:14 +0200

    On 4/04/2014 3:11, Brad Morris wrote:
    > Anon, like me, can see no use for the up arrangement of the pentaprism.
    > I still don't understand why Nicolas would do that.  He's a bright
    > fellow, I'm sure he had a reason.
    
    It's a surveying sextant, meant to be used horizontally.
    
    If a sextant's normal range is -5° to 125°, the range with the
    pentaprism 'pointing down' will be 85° to 215°, so if the prism were
    fixed you wouldn't be able to measure angles smaller than 85° without
    unscrewing the prism housing from the frame.
    
    With the pentaprism in the other position the range will be -95° to
    35°, returning the ability to measure angles smaller than 85°.
    
    Both the C&P and Freiberger pentaprism attachments can be rotated 90°,
    of course:
    
    http://www.cassens-plath.de/katalog/index.html?startpage=90
    http://www.fpm.de/index.php?c=1&s=pentaprisma
    
    Luc
    

       
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