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From: George Huxtable (no email)
Date: Sun Sep 12 2004 - 07:19:46 EDT
Frank Reed wrote, about Cotter's "A history of nautical astronomy"-
>As far as the book's contents, it's a good history but not great. Overall, I
>would grade it a solid B. The choice of topics is a little haphazard, and it's
>focused on mathematical theory rather than real practice at sea. For example,
>there's a nice chapter on altitude corrections with several equations
>derived, but, if I remember correctly, there's nothing on the 12/20 rule
>(which Henry
>H mentioned in another recent message on the list) that was so popular in the
>early 19th century.
Response from George-
Well, as far as altitude corrections are concerned, it's rather worse than
that! In many (interesting) pages about how the refraction corrections were
refined, nowhere is it clearly stated whether refraction should be added
to, or subtracted from, the measured altitude (it should be subtracted, of
course!).
But the point that I think Frank is missing about Cotter's book is its
uniqueness. Even though it has many deficiencies, nobody else (that I know
of) has put together a volume like it, where so many different navigational
procedures have been searched out, noted down in detail, and analysed in
terms of how they work.
Gordon Talge has told us he likes to consult the original manuals, but few
of us have easy access to that sort of library. And faced with the sort of
recipe supplied (by authors of lunar-distance clearing methods, for
example) it's not easy for people like me, with weak trig. ability, to
unravel such wording into a mathematical explanation, in modern notation.
I'm a fellow who likes to understand what's going on under the bonnet
("under the hood", I think, in American), a trait I seem to share with many
Nav-l subscribers.
Recently, there's been discussion about Mendoza's approximate method, and
Henry Halboth has raised Arnold's rather similar procedure. Although Cotter
discusses neither of these, by referring to his detailed explanation of
Merrifield's method (pages 227 to 231) it was possible to fathom just what
Mendoza and Arnold were up to. Without that analysis, I wouldn't have known
where to start, from their own explanations.
So in spite of its many defects, Cotter is the book that's taken down from
my library shelves for consultation, perhaps more than any other. It's also
liberally coated with my pencilled comments: something I dislike doing to a
book, which will infuriate its next owner when I'm dead-and-gone. That
reflects those aspects of the navigator's business that particularly
interest me, of course. You may have different priorities.
George.
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contact George Huxtable by email at , by phone at
01865 820222 (from outside UK, +44 1865 820222), or by mail at 1 Sandy
Lane, Southmoor, Abingdon, Oxon OX13 5HX, UK.
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