I'm standing in front of Stefanikova Observatory on Petrin Hill in Prague. On a clear night like this I should be able to see hundreds and hundreds of stars. As it is I can only count several dozen. The reason? Light pollution. Our modern civilisation simply produces too much light which outshines the stars. Experts say that too much light at night can disturb our natural rhythms. Improperly aimed and poorly shielded lamps can be dangerous for drivers and even pilots. Astronomers are badly affected as well as light pollution greatly diminishes the view of deep sky objects.
Astronomer Petr Sojka has worked here at the Petrin observatory for thirty years. Your observatory is located almost in the centre of Prague, close to the brightly lit Prague Castle and the Petrin Tower. How does it affect your observations?
"The buildings you have mentioned affect only a minor part of our observation. For instance, the Prague Castle is located north of our observatory but we observe most of the interesting astronomical objects and phenomena above the southern horizon. So the Prague Castle does not affect our observation. But the whole city affects the observation very much. I came to the observatory in 1965 and in those times the sky was very dark. And for instance, I was able to take astronomical photos with a five-hour exposure time. A few years ago I tried to compare it. I took a photo with the same photographic plate. And after only three minutes the plate was overexposed by the city lights. So the illumination of the sky has increased many times and of course, this affects our observation."
And can your visitors see less than they could for example ten, twenty or thirty years ago?
"Yes, the number of objects accessible to our telescopes decreased very dramatically. Of course, we can observe the Moon, the planets, bright stars, but we are not able to show some faint objects like galaxies or nebulas. There is another case: in 1996 there was a very bright comet. When we observed the comet with a telescope, the picture was not as good as a naked eye view of this comet outside the city. So no telescope but good conditions is better than a telescope in the city."
And I imagine that even the street lamps around the observatory must be spoiling your observations...
"These lamps are relatively new here. They were changed two years ago and the type selected is the worst possible I can imagine. Most of the light is radiated in upper directions. It directly illuminates the lenses of our telescopes instead of shining downwards. Unfortunately, these lamps were selected not by experts on illumination but by the people responsible for the preservation of the historical atmosphere in the city and they probably never heard of the lighting diagram and so on."
In February, the Czech lower house passed what is known as the "dark-sky law". That has made the Czech Republic the first country to enact national legislation reducing light pollution. Currently, similar legislation exists in three other countries but only in the form of regional laws. I also spoke to Petr Harmanec who is the head of the Astronomical Institute of Charles University. He had done a lot to help the new law come into being.
What is light pollution and when did Czech astronomers realise something had to be done about it?
"Well, from the astronomical point of view, light pollution means you have background light which affects the darkness of the sky. It means that the whole sky has some radiation which is of course unpleasant for us because it represents a kind of real noise in our observations. I can say that astronomers not only in the Czech Republic but in general were aware of this problem for many years. However, the problem became really acute after 1990 for two independent reasons. One is that by that time new, very sensitive detectors were introduced to astronomical observations and when the borders opened we were able to buy or loan such detectors from abroad and especially those observation which are carried out with relatively small telescopes are only possible because of the very high sensitivity of these detectors. But the sensitivity is decreased if the light is bright, of course. And the other reason is that, of course, the new climate and the development of a free-market economy in our country brought many new enterprises and people started to run new pubs, new restaurants and discos. Many of them, unfortunately, around astronomical observatories and that was another immediate reason why we realised something had to be done about it."
And now the "dark-sky law" has been passed, do you expect things will change soon for the better?
"Well, it is necessary to say that a real change may only come when not only the law but all the regulations specifying the consequences of the law are prepared. Fortunately enough, the Environment Ministry is responsible for the preparation of such instructions specifying how to preserve the conditions and how to fulfil the law in practice. Two of our colleagues are members of a task force which is now preparing the text of this regulation. As far as I know, the text should be ready by June, which means it will only be approved by the new government after the elections. So because of these circumstances I do not expect that things will develop particularly rapidly. But on the other hand the very existence of this law gives us some opportunities to get into personal contacts with people running such light pollution establishments, like discos, and try to negotiate some reasonable deal with them even before we have the exacts regulation."
Many people have a reason to be afraid their business might be affected by the law. Vlastimil Kral works in advertising. His company produces neon pipes and illuminated billboards - another source of light pollution.
"We produce everything that uses light in order to promote a product or a company. Be it neon pipes, lit-up billboards or panels. Light is a very powerful medium and at night it improves the look of things - and everything that's nicely illuminated appeals to people. Because advertisement is meant to appeal... Even lighting up buildings is a kind of advertisement. For example, if a building is nicely lit up, you will notice it immediately in a block of equally pretty buildings, or you will quickly find a department store if you see its neon ad on the roof. That's how this kind of advertising works... We don't know yet how exactly this new law will affect our business. Frankly, we always had to face problems, regardless of any law. But it was mainly in residential areas where people complained about bright ads shining into their windows."
Opponents of the law say it will cost too much to replace old wasteful lamps with properly shielded ones and many people are afraid that less light in the streets will encourage crime. But better lamps will save us a lot of energy which is good news for environmentalists and towns but bad news for power distributors. Well, it's hard to guess now whether some kind of compromise could be reached. But in a few months a lot of things will be clearer or shall I say, darker.
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