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Thank you. When I went to the link it costs $15.00 to download the if you
are a member and $22.00 if you are not. I'll take your word for it and
thanks to Lu too.
I've said it before and I'll say it again, this group is such a valuable
resource.
PS. if you have the article and would like to share it I would like to read
it.
----- Original Message -----
From: "Alexandre E Eremenko" 
To: 
Sent: Thursday, January 04, 2007 7:52 PM
Subject: [NavList 1979] Re: refraction


>
>
> 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.
>
>
>
> >
>
>
> --
> No virus found in this incoming message.
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> 1:34 PM
>
>


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