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    Re: Mysterious celestial measurement
    From: Luc Van den Borre
    Date: 2016 Jul 1, 16:50 +0200

    On 01/07/16 15:43, Ed Popko wrote:
    > What could this person possibly be measuring? Artistic license for sure.
    
    Looks pretty ok to me!
    
    It's a Jacob's staff with three cross pieces. He seems to be sliding the
    first piece against a scale on the staff. The other sliders don't
    obstruct his view of the bottom and top of the first cross piece. What a
    bother it is to remove them if one doesn't need to! In the dark you'd
    probably step on one and break it.
    He's holding it in a reasonable way, I think.
    
    Search for 'radius astronomicus'.
    
    The idea of the different sliders is to increase the range of the
    instrument. A smaller slider can measure smaller angles against the same
    scale drawn on the stick.
    
    http://www.dehilster.info/navigational_instruments/1661_kronan_cross-staff.php
    
    Luc
    
    

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