Figure 4. Comparison of 5^th to 95^th percentile in sky brightness.

The extremes in sky radiance are shown for all sites at all periods of astronomical night. A dashed 1:1 line is shown for reference; points on this line would have zero variation in sky brightness under all weather conditions. Locations which have 5th percentile values below 1 NSU likely indicate that the sky is darker when overcast.