... the partial phase about 6:30 Eastern Standard Time, and
totality lasts from 8:06 to 8:31 EST ..
For those who can, please try to note the time at which totality
starts -- that is when the last bright part of the moon vanishes and
the moon becomes dark over all. I wonder how close together
naked-eye measures are.
The reason I am asking is that I've read that the ancient Chinese used
the time of initial totality as a way of measuring longitude: by
measuring the angular height of a star above the horizon, people a
long distance apart -- 1000 km -- or more can find out how far east or
west the one is from the other. However to do this, the two observers
must make their measurement at the same time. A millenium ago, before
telescopes or telegraphs, the only event that was moderately
predictable and that would show the same time to everyone on the
moon-facing side of the planet would be the time of initial totality.
But I don't know how definitive that time is -- is it a vague sense
that the moon has entered totality that occurs over minutes, or is it
fairly sharply defined, within half a minute or less?
If the latter, then longitudes could be computed fairly accurately --
within say 25 km over 1000 or more km -- and maps could be drawn up.
(Of course, this method only works for cartography, not for ships
determining their location when at sea. A ship board captain could
make an observation, and then after he got to port and compared it
with other observations, determine what is longitude was when he made
the observation.)
Any how, I am curious how accurate this pre-telescopic,
pre-chronometer method is.
Thanks!
--
Robert J. Chassell Rattlesnake Enterprises
http://www.rattlesnake.com GnuPG Key ID: 004B4AC8
http://www.teak.cc [EMAIL PROTECTED]
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