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From: Peter Fogg (no email)
Date: Sat Jun 04 2005 - 05:56:27 EDT
George Huxtable wrote-
> To answer Bill's question, if a time-sight is taken at the moment when the
> Sun is due East or due West of the observer, then his latitude isn't
> needed at all in calculating local time-by-the-Sun. But that can only
> happen in the Summer months.
This is true, although what George hasn't added, perhaps considering it
assumed knowledge: The resulting position line (LOP) is the longitude.
As George has noted, it can be married with a noon sight (if moving; via a
running fix) to give an elegant 2 body fix, of a line of latitude and
longitude each. The accuracy is dependent (apart from the usual issues) on
how well the movement between the two sights can be plotted (run forward).
> To my mind, finding latitude at noon is a trivial matter that presents a
> problem only when the sky is cloudy at noon.
Well, its not trivial in latitudes where the sun approaches the zenith. It
tends to be more difficult generally to make observations of bodies near the
zenith. Its about the only time when having a good idea of the azimuth by
observation (a corrected compass reading) is problematical. Plus the sun in
full tropical mode plus the awkward contortions of trying to take a sight of
the blazing sun with the head tilted back at 90 degrees to the body, the eye
sockets filling with sweat - mean that noon sights in such places may be
notable by their absence.
> >Perhaps the fact that "longitude by noon sun" comes up so often
> >is a good reason that there *should* be a discussion of this
> >method, pointing out why it is a bad idea...
Nah, its all grist to the mill. There's nothing good or bad, as Shakespeare
said, only thinking makes it so ... If it serves a useful function (at least
when it comes to nav) then its all good. Not perfect, mind. Good is simply
good.
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