| The night sky brightness, together with number of clear nights, seeing, transparency, photometric stability and humidity, are some of the most important parameters that qualify a site for front-line ground--based astronomy. While there is almost no way to control the other characteristics of an astronomical site, the sky brightness can be kept at its natural level by preventing light pollution in the observatory areas. This can be achieved by means of extensive monitoring programmes aimed at detecting any possible effects of human activity on the measured sky brightness. |
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| Night sky at ESO-Paranal (Chile). Photo by L. Vanzi (ESO). |
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| Comparison between a night sky spectrum taken at Cerro Paranal-Chile during dark time (lower panel) and one taken in Asiago-Italy (upper panel). Light pollution is clearly visible in the form of Sodium and Mercury emission lines in the blue/visible part of the spectrum. |
| Night sky brightness data | FORS1 Night Sky Spectral Library |
| Not yet available | TAR file (17.5 Mb) Patat, F., 2008, Astronomy and Astrophysics 481, 575 |
