Sunrise is about 7am but it doesn't enter the cairn until about 10 mins after, official sunrise is about ten past 7 but since the view east from the hilltop is such low ground it makes it a little earlier. To get in to see the start of the illumination you need to be there at least half an hour early, maybe even an hour if you really want to see the early phase. The OPW try and get small groups in and out every 10 mins or so but you usually get in twice.