I always use USNO's site: http://aa.usno.navy.mil/data/docs/RS_OneYear.php
You can be simple and plug in something like "Grand Marais" in Minnesota, or use the second form and use actual coordinates. Note: The time on form one comes up as Standard Time, so add an hour.
For form two, you need to plug that in. EDT is GMT-4.
That's perhaps the one thing I don't care about mid-late Sept on the Isle. Beautiful color, but it does get darker early...