Table 1. Color levels used in the maps.

The first column gives the ratio between the artificial brightness and the natural background sky brightness (assumed to be 174 μcd/m²); the second column gives the artificial brightness (μcd/m²); the third column gives the approximate (that is, assuming a natural background of 22 mag/arcsec²) total brightness (mcd/m²); and the fourth and fifth columns give the colors.

Ratio to natural brightness	Artificial brightness (μcd/m2)	Approximate total brightness (mcd/m2)	Color
<0.01	<1.74	<0.176	Black
0.01–0.02	1.74–3.48	0.176–0.177	Dark gray
0.02–0.04	3.48–6.96	0.177–0.181	Gray
0.04–0.08	6.96–13.9	0.181–0.188	Dark blue
0.08–0.16	13.9–27.8	0.188–0.202	Blue
0.16–0.32	27.8–55.7	0.202–0.230	Light blue
0.32–0.64	55.7–111	0.230–0.285	Dark green
0.64–1.28	111–223	0.285–0.397	Green
1.28–2.56	223–445	0.397–0.619	Yellow
2.56–5.12	445–890	0.619–1.065	Orange
5.12–10.2	890–1780	1.07–1.96	Red
10.2–20.5	1780–3560	1.96–3.74	Magenta
20.5–41	3560–7130	3.74–7.30	Pink
>41	>7130	>7.30	White