[time-nuts] telling time without a clock
jimlux at earthlink.net
Wed Jan 25 23:45:10 EST 2012
On 1/25/12 8:38 PM, Jim Lux wrote:
> OK.. without getting into celestial navigation, the whole thing of
> telling time with the moon is intriguing. And with some forethought and
> data available today, we could fairly easily do what folks back in the
> 18th century could not.
> Let's say you run a suitable celestial model and identify all the
> reasonably bright and identifiable star that the moon occults in a given
> day. The moon moves about 1/2-1 degree per hour against the star field,
> so the question is, could you find, say, a star every couple hours.
> Then, assuming you know *about* what time it is, say, 930PM, you can go
> to your table, see that the Moon occults zeta obscuris at 2143. You sit
> there with your binoculars and watch the moon, and when zeta obscuris
> disappears, you know it's 2143. Done.
> You could even do it automatically with a not very accurate "goto"
> telescope and a camera (you just have to be able to point to the correct
> limb of the moon and look for the star).
> This kind of search would be incredibly tedious if you didn't have
> automation to help, but today, with reasonably accurate star catalogs
> AND reasonably accurate numerical ephemerides, it should be possible to
> make a "time almanac" with a page for each day, etc.
> (obviously, this only works about half the day, when the moon is up)
And, you should be able to make it work on any planet, as long as it has
moons (and you have the ephemeris known well enough.. not guaranteed by
Further, it occurs to me that if you know exactly what time it is AND
you know the elevation of the moon and the star it's occulting, you know
your lat and lon. I think..
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