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Table 4 Modeled zenith sky brightness at major astronomical observatory sites. For reference, the nearest population center(s) is listed, along with projected growth and predicted impact on zenith sky brightness for a linear dependence

From: The growing threat of light pollution to ground-based observatories

Observatory Longitude Latitude Milli-candela Fractional increase Urban Source 2010 Decadal %age Projection to
  per sq m over 22.0   Population Growth 2027
Hanle 78 57 51 32 46 46 0 0.000     0.000
Ali Tibet 80 01 00 32 19 00 0.00016 0.001 Shiquanhe 20,000   0.001
Paranal/Armazones − 70 24 17 − 24 37 38 0.00021 0.001 Mines?    0.001
HESS 16 30 00 − 23 16 16.8 0.00029 0.002 Windhoek 325,858 40 0.002
SALT 20 48 38.44 − 32 22 33.62 0.00034 0.002 Sutherland + Mines 2,841   0.002
Siding Spring Obs 149 04 01.92 − 31 16 31.44 0.00046 0.003     0.003
San Pedro Martir − 115 27 49.32 31 2 38.04 0.00068 0.004 Ensenada, Mexicali 689,775 0 0.004
McDonald − 104 01 21 30 40 17 0.00194 0.011     0.011
Las Campanas − 70 41 33.36 − 29 00 52.56 0.00196 0.011 La Serena 192,177 36.4 0.015
Mauna Kea a − 155 28 23 19 49 32.2 0.00344 0.020 Hilo 36,402 24.5 0.025
Lowell Discovery Telescope − 111 25 20 34 44 40 0.00645 0.037 Phoenix 4,192,887 28.9 0.048
El Leoncito − 69 17 44.16 − 31 47 54.96 0.00737 0.042 San Juan 715,052 13.9 0.048
Cerro Tololo Int Obsb − 70 48 23.49 − 30 10 10.78 0.01074 0.062 La Serena 192,177 36.4 0.084
Gran Tel Canariasc − 17 53 31.3 28 45 23.8 0.01259 0.072 Santa Cruz de La Palma 17,128 − 5.9 0.068
Kitt Peak − 111 35 48 31 57 30 0.01459 0.084 Tucson 980,263 16.2 0.097
Mt. Graham − 109 53 31.25 32 42 04.69 0.01642 0.094 Tucson/Phoenix 4,192,887 28.9 0.122
Apache Point Obs − 105 49 13 32 46 49 0.02233 0.128 Alamagordo 63,797 2.4 0.131
Mt. Hopkins − 110 53 07 31 41 18 0.03317 0.191 Tucson 980,263 16.2 0.222
Calar Alto − 2 32 46 37 13 25 0.03468 0.199 Almeria 695,560 34.2 0.267
VERITAS − 110 57 07.77 31 40 30.21 0.03492 0.201 Tucson 980,263 16.2 0.233
Xinglong 117 34 30 40 23 39 0.04962 0.285 Xinglong, Beijing 19,612,368 44 0.411
Palomar − 116 51 54 33 21 20.88 0.11031 0.634 LA/San Diego 3,095,313 10 0.697
Lick − 121 38 34 37 20 29 0.25914 1.489 San Jose 1,836,911 5.8 1.576
  1. aLight from Kilauea crater may cause overestimate of zenith sky brightness
  2. bTopographical blocking from coastal cities makes Cerro Pachon considerably darker, possibly by 3x
  3. cTopographical blocking from coastal cities makes the actual value of zenith sky brightness lower, possibly by 3x