A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Lewis and Clark Celestial Navigation Procedures
From: Greg Boyles
Date: 2002 Nov 24, 11:43 -0700
From: Greg Boyles
Date: 2002 Nov 24, 11:43 -0700
unsubscribe ----- Original Message ----- From: "George Huxtable"
To: Sent: Sunday, November 24, 2002 11:31 AM Subject: Re: Lewis and Clark Celestial Navigation Procedures > Arthur Pearson asked about the lunar navigation of Lewis and Clark. > > A reference appeared recently on this list to a paper about Lewis and > Clark's navigation, The paper was "The accuracy of the Astronomical > Observations of Lewis and Clark", by Richard S Preston, in Proceedings of > the American Philosophical society, vol 144, No 2, June 20000, pages 168. I > think it was available from a website but am sorry to say I have lost that > address. Arthur would find it a most interesting read. > > That paper referred to an Astronomy notebook kept by Lewis, which contained > instructions, in manuscript, written by the astronomer Robert M Patterson, > in the form of solutions to 5 "problems". > > I am most grateful to Bruce Stark (well known to this list), for sending me > a photocopy from a photographic negative of that Patterson document. It had > many flaws which made it difficult to read, but I have completed a > transcription to make it more readily understandable to the reader. I have > added a detailed commentary to explain aspects of the document to a modern > reader who is familiar with celestial navigation but unfamiliar with the > concepts and practices of the early 1800s. > > This has been written in two parts as two separate emails: the first > dealing with solutions to problems 1 to 3 and the second with problems 4 > and 5, and both these documents need to be taken together. These are long > emails (and Lewis and Clark may be a minority interest) so I will not > burden the Nav-L list with them (but if anyone asks for them to be posted, > I will). Instead, if anyone interested contacts me off-list, I will be > happy to send a copy directly. If any readers would like to check this > stuff out and inform me of errors or flaws, that would be appreciated. > > Arhur says- I am particularly curious > >about how closely their methods conformed to our recent discussion, "Re: > >Use of Sun Sights for Local time, and Lunars for Longitude". > I can say that Patterson's writeup has helped me to understand how the > altitudes of the bodies involved in a lunar can be calculated rather than > measured. > > It seems that Lewis and Clark always omitted to measure altitudes for their > lunars, and instead left them to be calculated at a later date. In that way > they could avoid setting up a reflecting pool, which would otherwise have > been necessary for their lunars. > > It appears from the Preston paper that some of their latitude observations > were greatly in error, which might imply that their use of a reflecting > pool was somewhat error-prone. However, I have made no further > investigations of my own into the Lewis and Clark results, nor have I seen > the Ambrose book. > > George Huxtable > > ================== > Arthur Pearson said- > > >Ladies and Gentlemen: > > > >I am interested in learning more about Lewis and Clark's navigational > >procedures. There has been some tangential mention on this list about > >their lunar methods of obtaining longitude. I am particularly curious > >about how closely their methods conformed to our recent discussion, "Re: > >Use of Sun Sights for Local time, and Lunars for Longitude". Stephen > >Ambrose's book "Undaunted Courage" provides glimpses into how they > >worked, including the following: > >* In Philadelphia, 1803, Lewis acquired "A Practical Introduction > >to Spherics and Nautical Astronomy" and "The Nautical Almanac and > >Astronomical Ephemeris" as well as "tables for finding latitude and > >longitude" (p. 91). > >* At one location along the Missouri, Lewis "measured the distance > >between the sun and the moon's nearest limb forty-eight times.. He > >faithfully recorded whatever he could whenever he could, leaving up to > >experts back east to work out the meaning of the figures" (p. 148). > >* Ambrose states that "...he wrote a thousand-word description of > >the instruments he was using, how he was using them, what he was > >measuring, and so forth. It seems Lewis wanted to be as sure as he > >could tat someone someday would take all his figures and make some sense > >of them." > > > >Has anyone on the list examined that thousand word description of how > >Lewis made his celestial observations? Would the tables he acquired in > >Philadelphia have been Bowditch's recently published "New American > >Practical Navigator"? Is there an essay or paper anywhere on this topic > >of his celestial procedures? Any insight or direction to additional > >sources would be most welcome. > > > >Thanks, > >Arthur > > ------------------------------ > > george---.u-net.com > George Huxtable, 1 Sandy Lane, Southmoor, Abingdon, Oxon OX13 5HX, UK. > Tel. 01865 820222 or (int.) +44 1865 820222. > ------------------------------ >