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Dear Trevor:

On Fri, 5 Nov 2004, Trevor J. Kenchington wrote:

> Geoffrey's method would need a star catalogue
> but not necessarily an
> almanac.

I agree.

I can also add (If I understood what he said correctly)
that his method only gives latitude.
Not longitude.

I don't see how to find longitude having only star catalog.
(Even with a sextant).

He was talking of sailing N-S until some stars are visible
at zenith... and then (presumably) sailing E-W until you
hit the land.

This means he is determining only Latitude.

(This we can do with using Polaris
only, no star catalog, assuming, of course that I am in Northern
hemisphere:-)


> Determination of the zenith without a sextant is said
> to be possible by
> lying on deck, sighting up the mast, and visually averaging the position
> of the masthead against the sky.

I doubt the precision of this is high, but I never tried.
And apparently Frank did not mean very high precision.

Anyway, let's say we know how to detemine latitude.
By memorizing something about stars, Polaris, for example).
Maybe some people with good memory can even memorize the
Sun's declination:-)

But interesting what Frank had in his mind
when he was asking this question.

Alex.

   

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