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Re: Joshua Slocum's navigational methods
From: Frank Reed
Date: 2005 Apr 16, 19:17 EDT
From: Frank Reed
Date: 2005 Apr 16, 19:17 EDT
Dan H, you wrote:
"Since Slocum was an experienced see Captain of many years, and based on
his
writings. I would say he used Lunars more than once in his voyage."
writings. I would say he used Lunars more than once in his voyage."
I think it's important to distinguish Slocum's circumnavigation from his
earlier commercial voyages. The risk, whatever it may have been, was entirely
his own when he was sailing around the world. He had no schedule to keep, no
cargo to deliver, no crew to keep safe and secure...
And you wrote:
"He most likely use a book of trig tables at best for his
calculations."
That's what one would normally use for celestial navigation, lunars or
otherwise, in that era. Or is that what you meant? Those trig tables would
be found in any of the standard navigational manuals of the era. Perhaps he had
Bowditch's "Practical Navigator" or more likely Norie's "Epitome of
Navigation" (since it's established that he taught himself navigation
originally --decades earlier-- from Norie).
And:
"It seems that how many times on a passage he would use lunars would depend
on his confidence in his current Dead Reckoning position."
Perhaps that's the point. Today we are taught that DR was a miserable
burden for early navigators who were always hopelessly uncertain of their
positions because DR was all they had. But the facts seem a little
different. Navigators cherished their dead reckoning. It was the mark of a true
mariner that he could sail an ocean by DR and scientific navigation "spoiled the
fun", you might say. It reminds me of the status of standard celestial
navigation today competing against GPS. The satellite systems spoil the fun, so
some navigators enjoy testing themselves by doing pure celestial (+DR when the
weather doesn't cooperate) to prove their mettle. The GPS is stowed away but
available if confidence fails. Ironically, a 19th century navigator might have
seen the finely honed and "scientific" methods of modern celestial navigation as
something like a GPS today --much too easy and given a few days 'anyone can do
it'.
And:
"He only mentions it once in the book"
He also explicitly states in his book that he kept his longitude mostly by
dead reckoning, which was why I originally asked if there was any other evidence
on the matter. Nonetheless, some people who have read SAATW find all sorts of
"clues" that they think point to extensive use of lunars. It looks
like wishful thinking to me...
And you wrote:
"but at least once at mid passage and again sometime before making land
seems prudent."
Sounds about right for a prudent mariner with cargo or lives at risk. Then
again, a prudent man would have gotten his chronometer repaired. Was
Joshua Slocum a prudent man? Did he have anything to lose besides self-esteem?
He was a man setting out to prove himself and make a little fame and money off
it if possible. He succeeded more or less, but I wouldn't call him prudent. Do
you remember reading in the book that he didn't know how to swim?
-FER
http://www.HistoricalAtlas.com/lunars
http://www.HistoricalAtlas.com/lunars