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Subject: Re: Visibility at rising and setting
From: Richard B. Emerson (navsys@XXX.XXX)
Date: Wed Apr 26 2000 - 09:24:29 EDT
Dr. Geoffrey Kolbe writes:
> As some on this list have pointed out, observation of celestial bodies
> setting, and particularly rising, are plagued with problems.
>
> However, I read somewhere of a yachtsman on a long voyage (may have been
> round-the-world) who observed stars at their zenith. He managed well enough
> to get safely around the Horn!
>
> Others on the list may be able to make more informed comment on this as a
> "no instruments" method of celestial navigation.
While somewhat "iffy" (judging the instant of meridian passage would
be a challenge), with the issue of refraction removed (compared to
judging the instant of true tangency to the horizon), the task is
somewhat easier.
Remember, too, that it's possible to obtain altidudes between the
horizon and zenith; specifically, through the use of a kamal
(basically a stick at the end of a bit of string). As I recall, a
competitor in the Marion-Bermuda race lost his sextant overboard(!!)
and navigated the race using a ruler as a kamal and sunglass lenses as
sun filters.
Rick
S/V One With The Wind, Baba 35
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