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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? 

Seriously, how accurate can an astrolabe be for its many "advertised" uses?

Bill

   

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