VMs: How did Ptolemy know about time zones

[Jorge Stolfi <stolfi@xxxxxxxxxxxxx>]

Rene,

I am not sure I undestand your current view of the Zodiac pages. Do
you feel that the events presumably encoded by the stars and nymphs
are all of the same type (e.g. all of them are star risings, all of
them are meridian crossings, etc.)? If so, perhaps we can match the
*sequence* of magnitudes inferred from the VMS with the sequence of
magnitudes of real stars sorted by longitude.

Or do you feel that some events are risings, some are settings, etc.?

  > [Elmar:] And this is exactly my question: How did he measure time
  > with the necessary accuracy? Or, which amounts to the same, how
  > did he synchronize events which were seperated by a considerable
  > distance? A rough estimate would assume a difference of some 15km
  > as the equivalent of 1', the smallest increment he would be able
  > to measure.

I don't know how he did it, but he *could* have confronted reports of
any event that was visible at two distant locations and whose timing
was sufficiently well-defined. A lunar eclipse should be adequate, I
think.  Or the Moon eclipsing a star.

Planetary conjunctions may be adequate, too, if measured with 
sufficiently precise instruments. Would it be possible at 
that time?

Was Ptolemy aware of planetary transits?

Solar eclipses obviously wouldn't work, because they are not
simultaneous; but perhaps they were thought to be...

All the best, 

--stolfi
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