NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Lunars Tables
From: Andr�s Ruiz
Date: 2007 Dec 4, 07:59 +0100
From: Andr�s Ruiz
Date: 2007 Dec 4, 07:59 +0100
Yes Frank, The cosine formula has two, maybe more, historical forms: The Dunthorne�s, and the Young�s one, and of course are the same. One can derive from other by adding the trigonometric identity: cos2 x + sin2 x = 1 Andr�s -----Mensaje original----- De: NavList@fer3.com [mailto:NavList@fer3.com] En nombre de frankreed@HistoricalAtlas.net Enviado el: martes, 04 de diciembre de 2007 3:55 Para: NavList@fer3.com Asunto: [NavList 4215] Re: Lunars Tables Andres Ruiz you wrote: "Both with the best method for clearing a lunar distance, for me: the Young�s formula." Ya know, unless you get into historical things, like working out the calculation by logarithms or maybe using tables of so-called "logarithmic differences," there's really no meaningful difference between "Young's formula" and the common cosine formula. They differ only by a trig identity. Once you put these calculations on a computer, they are identical (except for a very small difference in computation time, on the order of one microsecond for each cleared lunar). The attention given to Young's formula in Cotter's "History of Navigation and Nautical Astronomy," and repeated by some who have read that book, is completely out of proportion to its significance. Young's formula is a footnote in the history of lunars. This mistaken attention appears to be due to the fact that Cotter focused on publications from the period when lunars were obsolescent --post-1850. -FER --~--~---------~--~----~------------~-------~--~----~ To post to this group, send email to NavList@fer3.com To , send email to NavList-@fer3.com -~----------~----~----~----~------~----~------~--~---