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Frank wrote
Frank wrote:
> WHOA! er... Peter...?
> Yes, by watching the apparent movements of the stars (and knowing the day of
> the year) you can get a good idea of the local time, which is nice for
> planning your midnight snack. But without some instrumentality, like a
> sextant
> with an almanac for lunars or a chronometer, or some repetitive, predictable
> signal available over tens of thousands of square miles, like a satellite
> signal, there is no way to get any type of absolute time, and therefore no
> possible
> way to get anything but a very rough value for longitude astronomically, and
> no value at all that would be useful for navigation. Local time alone is
> useless for navigation. Yes, you can get a rough value for LATITUDE by
> watching
> zenith stars. But there's nothing in that technique that can supply
> longitude.
A novice question, and acknowledging your statement of "rough." Still, I'll
make a leap that "traditional navigation" is not limited to water. Would
the astrolabe and nocturnal (or some derivation) fall under" rough?"
If so, what happens to the souls of those using a rough instrument to
determine sunrise etc. and Mecca to pray? <g>
Seriously, how accurate can an astrolabe be for its many "advertised" uses?
Bill
