There seems to be somewhat of a mystery about when orbits were really proposed. Ptolemy clearly used the idea, which says no later than 150 BC, but I gather it's not clear how much older the idea was. I'm at work at the moment, and most of my history books are at home.
I did find this at NASA.
http://image.gsfc.nasa.gov/poetry/ask/a11846.html
And thank you for the scoop on the history of predicting solar eclipses!
I look forward to any light you can shed on the antiquity of Enoch. Hugs!