NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: refraction
From: Guy Schwartz
Date: 2007 Jan 4, 21:49 -0800
From: Guy Schwartz
Date: 2007 Jan 4, 21:49 -0800
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. > Checked by AVG Free Edition. > Version: 7.5.432 / Virus Database: 268.16.5/616 - Release Date: 1/4/2007 > 1:34 PM > > --~--~---------~--~----~------------~-------~--~----~ To post to this group, send email to NavList@fer3.com To , send email to NavList-@fer3.com -~----------~----~----~----~------~----~------~--~---