The location of the retreat is also in an area of about only 5% of the United States where the night sky is very little affected by light pollution. Colors correspond to ratios between the artificial sky brightness and the natural sky. brightness of :
<0.01 (black), 0.01-0.11 (dark grey), 0.11-0.33 (blue), 0.33-1 (green), 1-3 (yellow), 3-9 (orange), 9-27 (red), <27 (white).
Cinzano, Pierantonio. The World Atlas of the Artificial Night Sky Brightness.