On 1/24/12 10:26 AM, Chris Albertson wrote:
have you ever tried to measure an angular distance using a hand held
instrument while standing on the deck of a moving boat in the open
ocean? try it and you will see why they wanted a clock. You
really can't measure an arc minute reliably we should expect about 15
arc minute accuracy if you are standing on a moving ship. A few very
skilled people could do better.
The moon moves what? about 10 degrees per day so in practical terms
you can get time to about 30 minutes. But other sources of error
would add to that. But still knowing even the hour is very good
that puts you in the correct time zone
you can do much better than that by looking for occultations (and they
work with the new moon as well). If you know what day it is, you know
about where the moon is, and you can look up in a table which stars get
occulted when. Then you just watch through binoculars.
I'd say you can get within ten seconds without much trouble, assuming
you can find the star.
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