condition mean min max 4 h after light 6.4 6.4 6.4 8 h after light 5.45 4.7 6.2 12 h after light 6.75 6.7 6.8 4 h after dark 12.95 12.2 13.7 8 h after dark 10.3 9.7 10.9 12 h after dark 6.0 5.2 6.8