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    Re: Refraction at the horizon.
    From: George Huxtable
    Date: 2008 Mar 19, 20:50 -0000

    Marcel's graphs are plotted in terms of Zenith distance. But is this true
    zenith distance, or is it apparent zenith distance, after the light has been
    refracted?
    
    And whichever it is, if the plots were made instead in terms of the other
    one, and the ratios were computed for constant values of that other angle
    intead, would they look any different?
    
    Not that it would answer the problems. It's going to be hard to explain the
    very different amount of refraction change in response to a 10% increase in
    absolute temperature, and to a 10% reduction in pressure, either of which
    should have exactly the same effect on air density. If you made both those
    changes together, the air density should remain constant, and so the
    refraction should be unchanged. Judging from those graphs, that isn't going
    to happen. So the question needs to be asked- why the hell not? That may
    point to whatever's going wrong.
    
    George.
    
    contact George Huxtable at george---.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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