Citheronia regalis
Ventral View
This is a male moth as evidence by the "claspers" at the ventral end of the abdomen.
Sometimes called the Royal Walnut Moth
Hodges #7706
Unfortunately, these beautiful moths do not feed as adults and are therefore short lived.
It is a pleasant surprise to find one.
For more information on this species, see http://www.bugguide.net/node/view/313777
Auburn, Alabama