 Check out the bookstore at IRBS.com |
|
|
|
|||||
|
||||||
Subject: Re: Lewis and Clark Celestial Navigation Procedures
From: Greg Boyles (webmaster@XXX.XXX)
Date: Sun Nov 24 2002 - 13:43:48 EST
unsubscribe
----- Original Message -----
From: "George Huxtable" <george@XXX.XXX>
To: <NAVIGATION-L@XXX.XXX>
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@XXX.XXX
> George Huxtable, 1 Sandy Lane, Southmoor, Abingdon, Oxon OX13 5HX, UK.
> Tel. 01865 820222 or (int.) +44 1865 820222.
> ------------------------------
>
|