Great find, Brian. These are beautiful creatures and so big! I have only seen one on a misty night at Fraser's Hill in May, 2010.
There is a large saturniid in the tropical north of Australia and it is known as a Hercules Moth (
Coscinocera hercules). It is big but not as large as the Atlas Moth. I've seen it a few times near Mission Beach. Here is a scan of a really old slide (early '90s) of one that my kids and I found below a light on a dock one morning before heading out to the Great Barrier Reef.
Regards,