I dont think deer will always hit bait piles only at night. It seems to me later in the season after theyve been hunted is when they hit the piles after dark. I have lots of pics of deer hitting corn during daylight up until gun season typically then they become more nocturnal or cautious about hitting the piles during daylight hours. Just like I see deer come out to feed in fields during daylight is much more common early in the season, after gun season its rare to see deer come out to the fields to feed in light.