NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: from a watcher
From: Dan Allen
Date: 2002 Oct 17, 21:25 -0700
From: Dan Allen
Date: 2002 Oct 17, 21:25 -0700
On Thursday, October 17, 2002, at 08:11 PM, David Weilacher wrote: > cos(c) = cos(a)*cos(b) + sin(a)*sin(b)*cos(ab) > Isn't this the flatlanders side-angle-side trig formula. No, it is the spherical law of cosines. It is the most fundamental formula in celestial navigation. One can use it to determine great circle distances and courses, do sight reduction, measure the length of twilight, and many other useful things. The first chapter of W. M. Smart's classic "Textbook on Spherical Astronomy" is all about this formula and how it is derived and used. If you understand this formula and how to use it, you can do much of sight reduction in your sleep. It is not a difficult formula and it is worthy of everyone's study. Gee, that sounds rather pedantic, but it really is handy in any case. Dan