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    Re: sextant index error measurement
    From: Bill B
    Date: 2006 Nov 09, 02:56 -0500

    Frank wrote:
    > Just for fun, let's imagine an extreme exception... Take your sextant out to a
    > parking lot with nice black asphalt surfacing on a calm summer day just after
    > sunrise. Set it up vertically just above the surface and wait. As the Sun
    > heats the surface a layer of hot air will form over the parking lot. Without
    > wind, the hot layer will not immediately mix fully with the cooler air above
    > it. The density gradient will be substantial, and the refraction will be
    > measurably different. As the doctor says in the old joke, "Vell, don't do
    > that!".
    Hence my caveat of a light breeze for the K-Mart parking-lot site.  But you
    do lend support to my after-market product. It is either a fan or
    compressed-air device that can be mounted on the sextant to mix the air in
    front of the sextant. 
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