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    Re: Flare artifact
    From: Bill Noyce
    Date: 2005 Jul 6, 09:06 -0400

    Are you saying the flare only appears when the sun is reflected in
    the clear part of the horizon glass?  It will be reflected off both
    the front and back surfaces there.  Normally that's not a problem,
    since these surfaces are parallel, and the fraction-of-an-inch
    difference in the light paths is negligible over 93 million miles!
    But if those surfaces are no longer parallel, or if the index
    mirror isn't perfectly flat (more likely IMHO), you could see a
    double image.
    
    What do you see without the telescope?  Does it depend on the
    altitude you're measuring?
            -- Bill
    
    -----Original Message-----
    From: Navigation Mailing List
    [mailto:NAVIGATION-L@LISTSERV.WEBKAHUNA.COM] On Behalf Of Jim Thompson
    Sent: Wednesday, July 06, 2005 5:35 AM
    To: NAVIGATION-L@LISTSERV.WEBKAHUNA.COM
    Subject: Flare artifact
    
    
    My sextant has developed an annoying flare artifact.  It appeared the
    other
    day when I was doing sun sextant shots on a very bright summer forenoon.
    I
    was using a split mirror and the 6x telescope (Astra IIIb)  The flare
    appeared around the right half of the sun when the sun's image was in
    the
    left side of the field of view, but vanished leaving a clean image of
    the
    sun if I moved the sextant so the image was over the black half of the
    field
    of view on the right.
    
    I cleaned all the shades, the horizon glass, and both external surfaces
    of
    the telescope's lenses (ie front and back), but no imrovement.
    
    Any suggestions?  Sounds to me like I might have a problem inside the
    telescope.
    
    Jim Thompson
    jim3 at jimthompson dot net
    www.jimthompson.net
    --------------------
    Outgoing email scanned by Norton Antivirus
    
    
    

       
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