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Argh,

I wasn't going to say anything about Werf's article, but can't resist.

Werf appears to be simulating Slocum's lunar, perhaps in part to assess
Werf's, hypothesis that Slocum confounded civil and astronomical times
when taking values from the Nautical Almanac, and that this was the
error Slocum discusses in his book.  However, I could find no places in
Werf's simulation where he addresses this hypothesis, by taking a
logical value from the the Nautical Almanac and coming up with a
longitude a few hundred miles different from Slocum's.

Werf's paper did a service by presenting descriptions of some of the
classical means of clearing lunars.

Now I know we're not going to get anywhere arguing back and forth about
how many lunar's Slocum performed, but I see no reason to support
Werf's hypothesis more than Slocum's own statements that there was an
error in his logarithm tables.

If _one_ person would like a copy of this paper, I will send it to the
first request.

Fred

On Jan 12, 2004, at 4:41 PM, Frank Reed wrote:

> In the Spring 1997, in "Navigation: Journal of the Institute of
> Navigation" there is an article by Siebren Y. van der Werf  of
> Groningen, Netherlands entitled "The Lunar Distance Method in the
> Nineteenth Century: A Simulation of Joshua Slocum's Observations on
> June 16, 1896". Herbert Prinz was kind enough to send me a copy of
> this article. It's a shame it's not more widely available. Maybe
> someone could contact the copyright holders and arrange publication on
> th web.
>
> Van der Werf's article is more than an analysis of Slocum's
> observations. It's a meditation on Slocum's use of lunars and a nice
> general account of the method of lunar distances and the mathematics
> required to clear a lunar. Van der Werf agrees with my sense that
> Slocum shot no lunars on his voyage until that June afternoon in the
> Pacific that Slocum describes so delightfully in his book. He also
> agrees that Slocum was probably just confused when he talked about
> discovering an "error in his logarithms". Van der Werf also agrees
> with some of the people on this list who felt that Slocum probably
> shot lunars at least occasionally while crossing the Indian Ocean.
>
> In his article, van der Werf provides an interesting speculation on
> Slocum's "wrestling with tables". Several people on this list pointed
> out that Slocum should have been experienced with lunars so any
> "wrestling" would seem a bit odd. Van der Werf notes that Slocum would
> never have had a need to do this type of lunar before in which the
> longitude follows directly from the lunar and a nearly-simultaneous
> time sight. In all earlier cases, he would have been using lunars to
> correct a chronometer. So the idea that Slocum might have been
> confused and might have mistaken his own confusion for the "error in
> the the logarithms" that he reports is understandable.
>
> I would recommend van der Werf's article to anyone interested in
> lunars. It's a nice "meditation" and it's well-written. I don't want
> to break the Institute of Navigation's copyright, but I think it's
> within fair use to pass along a photocopy to one other person. Claim
> it first, and it's yours!
>
> Frank E. Reed
> [X] Mystic, Connecticut
> [ ] Chicago, Illinois

   

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