I went in right at first light last Sunday morning, shot a doe about an hour later. One day last year i overslept, it had been light for at least 45 minutes. I hurried up and snuck in there very quietly, seen 4 bucks that morning. One of the better mornings i had. Normally, i try to get in there just before light, but getting in there right at light or a little after has never ruined any hunts for me either.