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On Thu, 4 Jan 2007, Guy Schwartz wrote:

> 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?

The principle is easy.
Positions of stars (and motion of Sun)
were known since long ago.
With higher and higher precision gradually.
Taking their apparent altitudes and comparing with
computed altitudes you can find refraction.

I don't know precise historical details, but I am sure
that Ptolemy was well aware of refraction.

The theory explaining refraction is of much later origin
probably of XVII century. Once you derive a formula
on a theoretical basis, you need only few precise
observations to determine numerical coefficients in this
formula and to test the theory. The modern tables
are computed using this formula.
(I compared the formula with the Almanac, it matches:-)

I wanted to finish this message with the words
"But I do not know the precise history of events"
but then I typed on Google:
atmospheric refraction history
and the first site which popped up was:
http://www.opticsinfobase.org/abstract.cfm?id=85182
with the paper
Atmospheric refraction: a history
by Waldemar H. Lehn and Siebren van der Werf.
The full text is downloadable in PDF (for me)
but I am not sure that it is downloadable for everyone.
If not, tell me and I will e-mail you the paper.

Rare luck! Usually Google returns 175,000,000
sites with total irrelevant junk when I search:-)

Alex.



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