That's because precise calculation of the positions of the planets-
including Earth- is only possible for a few thousand years. Beyond that,
the chaotic nature of orbital dynamics in a multiple body system becomes
dominant. No software, professional or amateur, can provide an accurate
topocentric sky map for more than a few thousand years either way from
the present.
That is quite different from estimating the shapes of asterisms over
time. In most cases, the proper motion of the brighter stars is well
known, and makes it possible to know what constellations will look like
over periods of millions of years. But since the purpose of sky charting
software is primarily to produce accurate topocentric star maps, they
generally limit themselves to a much shorter period. They won't let you
look at the Big Dipper 100,000 years ago, not because they can't
accurately render it, but because they can't accurately position the
entire asterism in the sky.
Chris
*******************************
Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com
On 9/12/2011 5:20 AM, karmaka wrote:
Hello Robert,
thank you for the interesting images.
The depiction of the 'Big Dipper' 100.000 years ago matches other
simulations and depictions I've seen so far.
Precise calculations with astronomical software for amateurs are usually only
possible
until a few thousand years back in time. There must be a reason why.
'Redshift 7 Premium' for example allows only calculations which do not go back
further than 4713 BC.
Best regards
Martin
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