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    Re: Lunar Distances with Alex's SNO-T
    From: Bill B
    Date: 2006 Oct 31, 16:50 -0400

    I located the Frank's post.  "RE: Refraction for beginners" 7/9/04
    Frank wrote:  "It's interesting (well, as interesting as this sort of stuff
    can get ) that the percentage change (as opposed to the additive change)
    is nearly the same at all altitudes. If you climb 1600 feet into the
    atmosphere from sea level the pressure drops just about 5%. If you write
    this new pressure down and climb another 1600 feet, the pressure drops by
    just about 5% from that new pressure you wrote down. Even at 50,000 feet, if
    you climb 1600 feet, you will find that the pressure at 51,600 is lower by
    nearly 5% from the pressure you left behind at 50,000. This happens because,
    from a mathematical point of view, the density of the atmosphere drops
    exponentially with altitude roughly according to the formula
       (density at height h) = (density at sea level) * exp( - height /
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