General – Lets Talk about light pollution

Light pollution – a global problem

80%¹ of  earths human population suffers from light pollution, in Europe and the USA even 99%¹. The animal wild life suffers even more, and also plants are reported to be influenced by light pollution¹.

But what is light pollution? In the past this term was only known by the group of persons which are directly affected by it: astronomers and biologists. But the greater public didn’t know the term. But in the last few years, the problem has grown so big, it has even broached in mainstream media.

Light polluted sky over Linz. Taken 30 km south of Linz near Aschach an der Steyr on 12.04.2013. The light pollution increased since. (Photo by Sternfreunde Steyr, Infos about light pollution and the original image can be found here)

Light pollution basically is the presence of anthropogenic light in the night environment². It is created by extensive use of artificial light, such as street lamps, building illumination, etc.

And what are the negative effects of light pollution?

First of all, the lit night sky affects our very own metabolism and psychology². But not only humans suffer from light pollution, so do the animals. And here foremost the insects. You only have to look at a street lamp — you immediately see myriads of insects buzzing around the light. They get trapped in the light, or burned by the very hot light source or just forget to feed and mate. Another less known fact is, that light pollution also has an effect on plants. Plants also rely heavily on the natural day-night cycle which is interfered by the artificial lights.

And of course we astronomers suffer from it, because the free sight to the stars is taken away from us. The artificial light is so powerful that it easy outshines the very faint objects in the sky. In densely populated areas, it is even so strong, that you struggle to see any star at all!

Star Park Hohe Dirn – a perfect sky

The Star Park Hohe Dirn, the location of the KRO, is luckily (yet) a whole other story. We have all major cities in the north and shielded by a small rising ground behind the observatory. So Linz, Steyr, Wels, etc. are well shielded.

The other thing is the south: There are basically two national parks, the national park Kalkalpen³ and the national park Gesäuse³. So in the south there are just mountains and forests for about 120km (Graz). On the east we also have more or less hills and mountains until Vienna comes up in about 150km.

This geographical specialty can now be seen in a light pollution map of the region:

Light pollution map of Austria. The red circle marks the approximate location of the KRO. You can see, it is at the northern border of the very dark area. (Source:, original map can be found here)

Due to this circumstance we have chosen the spot for our star park and for the observatory.
Another lucky circumstance is the local seeing. Our visual observers with their huge dobsonian newton telescopes (> 20″) have reported seeing values from well below 0.5″! And this not just once in a lifetime — these values are achieved several times in a year.

¹Lichtverschmutzung –
²Light pollution –
³Detailed information on the national park Kalkalpen and Gesäuse can be found on the german Wikipedia pages of Nationalpark Kalkalpen and Nationalpark Gesäuse.



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