This is completely drool worthy! Ken Zeamon details his plans and procedure for making an orrery. He even has a downloadable file with the files for his CNC Sherline mill. Lots more detail and videos here: http://zeamon.com/wordpress/?page_id=526
My favourite part is the 7 months in 7 minutes video because it helps with getting an idea or procedure and method of operation. On his site he has more videos detailing each stage. But the overview is where to start!