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    Re: refraction
    From: Lu Abel
    Date: 2007 Jan 04, 19:11 -0800

    Not much different than measuring bending of the stick, Guy, except with
    a bit of patience required.
    If I track the rising or setting of a body, I should see a uniform rate
    of motion in the sky as long as refraction is insignificant.  Once it
    becomes significant, however, the rate should change.
    I could, for example, calculate the expected time a body would disappear
    below the horizon based on its motion through the sky.  But I would
    observe it to set later.  The time of observed setting would lead me to
    a value for refraction, ie, the amount the body is below the horizon and
    therefore the amount of refraction.
    Measurement of factors such a pressure, humidity, and temperature could
    then be used to refine the parameters.
    Lu Abel
    Guy Schwartz wrote:
    > Inserting a 4 foot stick half way into a big tank of water at a 45
    > degree angle, the refraction can be measured or closely approximated.
    > How were the refraction adjustments initially calculated for the atmosphere?
    > What was the methodology used? I don't think it was as easy as the stick
    > in the water method?
    > Thank you.
    > Guy
    > >
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