NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: finding your latitude through double altitudes (and elapsed time).
From: Frank Reed CT
Date: 2007 Apr 01, 02:07 -0700
From: Frank Reed CT
Date: 2007 Apr 01, 02:07 -0700
Hi Joel. You may want to get a copy of "Peirce's Trigonometry". Benjamin Peirce (yes, that's how he spelled it) was the mathematician who did most of the calculational work launching the American Ephemeris & Nautical Almanac back in the 1850s. He was a student, colleague, and great admirer of Nathaniel Bowditch. Like most textbooks from that era, the full title of "Peirce's Trigonometry" runs for half a page. The key part of the subtitle for this discussion is: "particularly adapted to explaining the construction of Bowditch's Navigator". And it lives up to that promise. Peirce explains the derivation of the vast majority of the trigonometric rules in Bowditch. Naturally, the language is that of 19th century math, so it takes some getting used to, but it's a helluva lot easier than trying to reverse-engineer the sparse rules as laid out in Bowditch and other navigation manuals from that era. Remember when finding old books was an adventure in dusty old bookstores? And then three years ago, it was an adventure in watching online auction sites? Well, the adventure is over. :-) There are 19th century editions of Bowditch online, and there are at least two different scans of Peirce's book. There's one on google books here: http://books.google.com/books?q=intitle:trigonometry+inauthor:peirce I believe the method you were asking about is outlined starting on page 198. -FER 42.0N 87.7W, or 41.4N 72.1W. www.HistoricalAtlas.com/lunars --~--~---------~--~----~------------~-------~--~----~ To post to this group, send email to NavList@fer3.com To , send email to NavList-@fer3.com -~----------~----~----~----~------~----~------~--~---
