(For some background of the Declaration text given below, see the http://amper.ped.muni.cz/light/declaration directory. To endorse its text individually, you may use a form at web77.eu/ida/.)

We, the participants of the 12. Symposium for the Protection of the Night Sky, held in Bielsko-Biala 13.-15. 9. 2012:

Urge the IDA and all relevant institutions to adopt a true (i.e., scientific) definition of Light Pollution,1 as light added artificially outdoors at night is a serious pollutant;

Urge all legislative bodies to allow no light going horizontally or upwards from outdoor lighting.2 Any arguments against it have been proven false by science long ago and by the excellent experience from countries with such legislation: Slovenia and most of Italian provinces;

Recommend the switching off of the lights or at least dimming them by three times or more when there are no or almost nobody to make use of them;

Stress that any surfaces with luminances 10× or more stronger than the road luminance, if in the field of view, are against the purpose of outdoor lighting, are uncomfortable for people and dangerous to traffic.3 This includes advertising and building illumination, among others;

Feel that having artificial illuminance, of windows from outside at night lower than 0.2 lx,4 is a basic human right.

Footnotes, that are not a part of the Declaration, but may make it understandable for a broader public:

1. The list of current, compatible scientific definitions of Light Pollution (Photopollution) is, starting from the newest, process-based one:

  1. Introduction by humans, directly or indirectly, of artificial light into the environment.
  2. Alteration of light levels in the outdoor environment (from those present naturally) due to man-made sources of light. Indoor light pollution is such alteration of light levels in the indoor environment due to sources of light, which compromises human health.
  3. Alteration of natural light levels in the outdoor environment owing to artificial light sources.
A thorough text containing the long indoor-outdoor definition is lp_what_is.pdf. An older definition, also compatible, but more prone to misunderstanding when used standalone (like ‘This is no degradation, but improvement!’), is See the Wikipedia item Light Pollution for the explicit sources of these definitions.

During daytime, pollution from outdoor lights would be so small relatively, even if the lights would be on, that it could be mostly neglected. The same absolute amount of pollution becomes relevant and then serious, when the natural light levels decline during twilight. The main problem with artificialy produced light concerns nighttime, of course.

2. See, e.g., http://amper.ped.muni.cz/light/EuP/FS.htm.

3. A comfortable range of luminances in a scene is 1:10. Luminance of a surface in a shadow is about 1/10 of that of a neighbouring sunlit surface with the same albedo. Deep black and brightest white, under common illuminance, have again this ratio of luminances. Sunlit white surface adjacent to a black surface in a shadow presents a complication to see details of the black surface. Any part of a scene, which has ten times larger luminance than the most important piece of the scene, is too conspicuous already; this may be tolerable for a white mark on a fresh black asphalt, but not for advertisements distracting the attention of drivers. Driving at night is more difficult than driving during daylight, and artificially overlit objects makes it even harder.

4. The strongest natural illuminance of a vertical window at night, due to full Moon, is never over 0.2 lx; levels reaching 0.1 lx or more concern less then one hundred hours per year (i.e., less than 3 % of deep night duration). Tolerating artificial illuminances of windows up to 0.15 lx is generous enough to enable street illuminances ten times the full moon ones even between 22 h and 6 h – these are sufficient for anybody to see the way and any obstacles very well. See more in a letter from 2007 and quantitative estimates in the next letter. Even 0.1 lx falling to windows is hundred times more than usual natural illuminance. And having natural silence and natural darkness during sleeptime is a human right for sure. It had been no need to fight for it in the past millions of years.