Hey, I saw this link in Cabelas' mag and thought I'd share it. Many may already be aware of it, but I'm sure there are some that will find it useful. In most areas, fall hunting usually starts 30 minutes before offical sunrise and 30 mins after official sunset. "Official" time is determined by the U.S. Naval Observatory. Check the site by adding your area information (about halfway down the page) and get offical sunrise/set times, moon times, etc.
http://aa.usno.navy.mil/data/docs/RS_OneYear.php
http://aa.usno.navy.mil/data/docs/RS_OneYear.php