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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
    fit
    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.
    
    Renee
    
    
    

       
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