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A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: No sextant, no watch, no almanach, nothing
From: Frank Reed CT
Date: 2004 Nov 8, 00:10 EST
From: Frank Reed CT
Date: 2004 Nov 8, 00:10 EST
Trevor K wrote:
"Geoffrey's method would need a star catalogue but not necessarily an
almanac. Since the stars are fixed (at the level of precision of
instrument-free navigation), the declinations of the brighter ones can
be learnt with relatively little difficulty. "
Right. And if it's acceptable to know that Polaris has a declination of nearly 90 degrees without an almanac, then surely it' acceptable to memorize a few more star positions. The funny thing is that the declinations of stars could be recovered very quickly by a knowledgeable person (on shore) without access to an almanac, but what about latitudes of places on Earth? It would easier to live without a star chart than to live without a map of the globe...
And:
"When on the intended parallel, those stars should of course be just
circumpolar, grazing the horizon at each inferior meridian passage --
something that could be observed with reasonable precision at tropical
and temperate latitudes."
I guess you could extrapolate to visualize that "grazing" motion, but stars are literally invisible within a couple of degrees of the horizon...
Frank R
[ ] Mystic, Connecticut
[X] Chicago, Illinois
"Geoffrey's method would need a star catalogue but not necessarily an
almanac. Since the stars are fixed (at the level of precision of
instrument-free navigation), the declinations of the brighter ones can
be learnt with relatively little difficulty. "
Right. And if it's acceptable to know that Polaris has a declination of nearly 90 degrees without an almanac, then surely it' acceptable to memorize a few more star positions. The funny thing is that the declinations of stars could be recovered very quickly by a knowledgeable person (on shore) without access to an almanac, but what about latitudes of places on Earth? It would easier to live without a star chart than to live without a map of the globe...
And:
"When on the intended parallel, those stars should of course be just
circumpolar, grazing the horizon at each inferior meridian passage --
something that could be observed with reasonable precision at tropical
and temperate latitudes."
I guess you could extrapolate to visualize that "grazing" motion, but stars are literally invisible within a couple of degrees of the horizon...
Frank R
[ ] Mystic, Connecticut
[X] Chicago, Illinois
