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A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Lunar distances
From: Eric Haberfellner
Date: 2002 Jan 25, 11:38 PM
From: Eric Haberfellner
Date: 2002 Jan 25, 11:38 PM
I am not an expert on Lunars, but I believe that Lechter gives a complete solution. He states: "In discovering a way to solve it [GMT by lunar distance] using only the Nautical Almanac and the ordinary sight reduction tables I had on board (H.O. 214), I experienced one of the great intellectual triumphs of my life. On the 25th day of the passage, with 500 miles to go, I was able to prove beyond all doubt that my clock was correct, within one minute of GMT, so my longitude was gound within 30 miles or so - ample precision for the upcoming landfall" This was in 1963. Did the Nautical Almanac still have Lunar distance tables at that time? I will have to dig into this material to figure out what information he actually uses from the Nautical Almanac. I don't have time right now. He has some equations, and gives complete examples. Eric Haberfellner -----Original Message----- From Navigation Mailing List [mailto:NAVIGATION-L@LISTSERV.WEBKAHUNA.COM]On Behalf Of Chuck Griffiths Sent: Friday, January 25, 2002 12:09 PM To: NAVIGATION-L@LISTSERV.WEBKAHUNA.COM Subject: Re: Lunar distances george@huxtable.u-net.com wrote: ...There's no escaping the fact that lunar distances are a complex business. If there existed accessible textbooks on the subject, I could have simply referred the reader to those. The only modern one I am familiar with is C.H.Cotter, "A History of Nautical Astronomy" (London, 1968), which is very hard to find. If any reader knows of other useful textbooks on lunars, please say. Eric Haberfellner tells me of "Self-Contained Celestial Navigation with H.O. 208" by John S. Letcher, Jr., published by International Marine Publishing Company in 1977. He says- "This book (to my suprise) has a chapter on "Time by Lunar Distance" and a chapter on "Time by Lunar Lines of Position". This would make it one of the few "modern" books that deals with this subject."... Which brings to mind the following: I'm curious whether anyone has an old enough edition of Bowditch to still have tables for clearing lunar distances. I believe that the tables and explanations were included until the mid-60's. What did these tables provide solutions for? My related question: Has anyone cataloged the tables and articles that have been removed from Bowditch over the years? I have to say, the 1995 edition, compared to the 1977 edition, seems to have left out a lot of good information e.g., correct plotting of high angle sights and the history of sight reduction techniques. If you start adding up just the few things that I'm aware of that have been taken out over the years - tables for clearing lunar distances, Ageton's tables, better explanations spherical trig, it seems like a collection of the "lost" Bowditch articles and tables would be a pretty nice reference to own. Chuck Griffiths ********************************************************************** This e-mail and any files transmitted with it are confidential and may be legally privileged or otherwise exempt from disclosure under applicable law. This e-mail and its files are intended solely for the individual or entity to whom they are addressed and their content is the property of Smiths Aerospace. If you are not the intended recipient, please do not read, copy, use or disclose this communication. If you have received this e-mail in error please notify the e-mail administrator at postmaster@si.com and then delete this e-mail, its files and any copies. This footnote also confirms that this e-mail message has been scanned for the presence of known computer viruses. ***********************************************************************