on animal behaviour, and human health be assessed.

This is the aim of our ongoing night sky brightness measurements in Vienna and at the “Leopold-Figl-Observatorium für Astrophysik” (LFOA) on Mount Mitterschöpfl. We complemented our measurements with spectroscopic studies of the night sky at the Vienna University Observatory, which hosts the “Institut für Astrophysik” (IfA).

It should be noted that all our measurements refer to scattered light. We measured only brightness values and spectra of the sky background, while we explicitly avoided to measure any direct radiation from streetlamps. This is what we call “night sky brightness” (NSB). In other words: the brightness values and the spectra presented in this paper refer to the total backscattered light of the night sky. Its origin is the whole ensemble of streetlamps, facade illuminations, illuminated billboards etc. at the respective observing site and in its near and far surroundings. The natural nocturnal radiation from the Earth’s atmosphere, which is produced by different processes such as recombination of atoms that have been ionized by the Sun’s radiation during daytime, contributes very little to the NSB that we measured at our observing sites, since the latter is dominated by the influence of artificial light.

Measurement sites 