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    Re: Off Center Sextant Scope Observations
    From: George Huxtable
    Date: 2007 Nov 24, 22:14 -0000

    Fred Hebard wrote-
    | As I recall when determining index error using the sun, the point of
    | contact varies with up and down location in the telescope.
    Response from George.
    How interesting! When Fred says "As I recall ...", is he going just by a dim
    recollection, or is it a real, reproducible effect, that he can see whenever
    he tries to repeat it? To me, it appears to defeat the laws of optics as I
    understand them, but that doesn't lead me to deny that Fred saw what he saw.
    It  makes it worth examining more closely to discover why.  Could it result,
    perhaps, from a mirror that wasn't exactly flat, so the reflection angle
    varies slightly when you use a different part? Or a shade with a bit of
    ripple in it? Tell us more, Fred.
    contact George Huxtable at george@huxtable.u-net.com
    or at +44 1865 820222 (from UK, 01865 820222)
    or at 1 Sandy Lane, Southmoor, Abingdon, Oxon OX13 5HX, UK.
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