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    Star sparkle in sextant image
    From: Jim Thompson
    Date: 2004 Sep 27, 08:48 -0300

    I am still working to get my intercepts down to acceptable distance from a
    known position on land or at anchor.  All too often I am about 2-4 miles
    away. Perhaps my biologics are against me?  Even when I think that I have
    perfectly lined up the sun's limb with a clear horizon, my sights tend to be
    out by that much at times.  Perhaps I cannot see the limb and horizon as
    clearly as my brain thinks it can.
    For now, though, I would like to explore star image quality.  We have
    discussed star sparkle before on this list, but I finally got around to
    attempting to draw what I actually seem to see.  Sparkle makes it difficult
    for me to precisely line up the star's images on top of each other. This
    means that I have to take a series of sights to obtain an Index Error before
    and after each round of sights, and then average them. Typically my
    variation in a series of IE attempts ranges to about +/- 0.5' of arc, which
    seems like a lot to me.  I would have thought that a navigator could expect
    less variation, say +/ 0.2' or even 0.1'?
    How do the images on the following page compare with what you see through
    your sextant?  Is there more sparkle, or less?
    Jim Thompson
    Outgoing mail scanned by Norton Antivirus

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