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On 2018-01-17 12:23, Mark Coady wrote:
> The case is that many antiquity structures are positoned to precise 
solar/lunar/star correlations.  Favorites include stonehenge roughly 2950 BC? 
and others aligned to summer and winter solstice events.
>   Is there a handyonline calculator that goes that far back?  So I could 
look at a true satellite shot with bearings vs actual angular position on 
that date in 2950 BC? Are there any accumulated earthquake/shock events on 
earth that might make any uniform calculator erronoeous by any signifcant 
amount?

I forget how far back JPL Horizons goes, but surely it can reach the era
of Stonehenge. It uses a special long term precession model for dates
before 1800 (I think) and the latest JPL long ephemeris, the DE431.

There's considerable uncertainty about delta T in the remote past, and
that's an issue for some ancient events. But it doesn't matter for
alignments, which deal with rise and set azimuths, and perhaps altitude
at culmination. These are a function of the direction of the pole but
not Earth's rotation about the pole.

Earthquakes don't seem to have any significant effect on Earth
orientation. Even after a major one, I see no bulletins from the IERS
regarding a jump in the polar motion and offset of the pole.

You'll probably get a more informed answer at the HASTRO-L (History of
Astronomy) discussion group.

   

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