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    Re: What is the Longest Lunar Possible?
    From: Alexandre Eremenko
    Date: 2013 Jan 21, 21:45 -0500

    Brad,
    1. Nothing was attached to your message.
    2. But I have Chauvenet anyway.
    3. That the instrument "becomes sensitive" near 180 is not
    the property of the instrument, this is the property of geometry of
    the sphere. Any instrument will become sensitive (and unstable)
    near 180.
    
    Alex.
    
    > Hi Geoffrey
    >
    >
    >
    > Attached, find an image of the optical path of the prismatic reflecting
    > circle.  Note that this is from Chauvenet and not a self generated image.
    > It shows the optical path (dotted line) at 180 degrees!
    >
    >
    >
    > I see how the instrument becomes sensitive at 180.  While the paths are
    > parallel, they are not colinear, generating parallax.  Additionally, small
    > displacements of the instru from the line between the two objects
    >
    >
    >
    > What then is your view on the largest possible measurable distance, as a
    > practical matter?  Should it be limited to 170? 165?
    >
    >
    >
    > Best Regards
    >
    > Brad
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    >
    
    
    
    
    

       
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