ancient druids' knowledge of astronomy?

What is known of the ancient druids' knowledge of
astronomy? And that of the peoples that preceded
them in the British Isles, e.g. those responsible
for Stonehenge and other stone circles?

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David Dalton http://www.nfld.com/~dalton (home page)
http://www.nfld.com/~dalton/nf.html Newfoundland&Labrador Travel & Music
http://www.nfld.com/~dalton/dtales.html Salmon on the Thorns (mystic page)
"Here I go again...back into the flame" (Sarah McLachlan)