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    Re: sextant precision.
    From: Renee Mattie
    Date: 2005 Jun 21, 21:30 -0400

    George Huxtable wrote -
    > If you put an angled slab of parallel glass, thick as you like, into the
    incoming path of light
    > before it strikes the index mirror, the only difference it will make is
    that the bit of incoming
    > sunlight sampled by the index mirror is displaced by a few millimetres.
    But, as it's everywhere
    > parallel, that sample of sunlight is just the same, travelling in exactly
    the same direction, as
    > before. The sextant won't notice any difference whatsoever.
    Oh yes, good point.  The sun is not a laser pointer and Earth's orbit won't
    in my closet.  Got it.
    I was thinking about viewing spots on the wall instead of viewing the sun
    through a telescope.  The nice thing about a laser is that it is a source
    of collimated light.  But even given a bright enough laser, it could be
    a bit tricky aligning everything within tolerance, using only what's already
    in the garage.  I have not done the math to compare the size of errors to be
    expected from misalignment of the test bed to the size of the errors George
    is looking for.

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