condition mean min max 4 h after light 1.8 1.8 1.8 8 h after light 9.5 9.2 9.8 12 h after light 7.35 1.0 13.7 4 h after dark 7.5 1.4 13.6 8 h after dark 2.5 1.8 3.2 12 h after dark 1.85 1.0 2.7