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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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