The term light pollution describes a phenomenon in industrialized countries, cities, locations etc. with high distribution of light-emitting devices like traffic lights, citiy lights, cars etc. in the human visual range. Mostly white and yellow light. This leads to outshine of visible stars and other objects in the night sky due to strongly reduced contrast.

But it has also dramatic effects on animals, plants and humans. Some animals for example show a shifted night-day rhythm which is often lethal for specific species.  (Fig. 1).

The Bortle scale (named after the american amateur astronomer John E. Bortle) is a nine-level numeric scale that gives an idea about the local light pollution. Ranging from 1 – low light pollution with very good seeing condition – to 9 – severe light pollution with strongly reduced night sky and star seeing due to low contrast.

The Scale was first published by Bortle in Sky and Telescope magazine in 2001.

In contrast to seeing scales the Bortle scale is predominately not based on artificial optical tools.

In Fig. 3 you can see Bortle scale indices of the corresponding areas.

BUT it’s also important to note that the Bortle scale is quite subjective. „Subjective estimates may not always be reliable or accurate“ (Human contrast threshold and astronomical visibility by Andrew Crumey, 2014)

). – It’s okay for a rough estimation of the local light pollution.

Therefore, cities and neighboring location show a high Bortle scale index of about 6-9. My current region is a 7-8 Bortle scale region (Fig. 2).

In contrast: The location of the Very Large Telescope (VLT) is practically not light light-polluted – Bortle scale 1 (Fig. 4.).

You can find informations of your regional light pollution in the internet.