September 26, 2013

searching for darkness in our night time: light pollution

Although the phrase of "light pollution" might have already slid through your ears some time, the artificial light at night is sliding through your windows to your eyes constantly!

Yes, that artificial, misdirected, obtrusive light, colouring our dark sky and hiding the constellations is called "light pollution" as it has negative effects on our health and on our ecosystem. There are various types of light pollution as there are various types of lights, leading to various consequences, but I am not going to write about it. Shortly one can loop up at wikipedia for more information.

Looking at this our created phenomenon from geographic perspective, it is interesting how the global light pollution mapping as well as non-polluted - dark-pitch area search is done.
Those topics are already tackled by astronomers all around the world. There are national as well as global projects and even organizations working on 'saving' the dark sky, like for example: Astronomers recently probably can't see the stars anymore and started working on searching areas where they could do their job at best and so they are creating the maps and conducting researches on finding the dark sky parks firstly!

The - international organization - provides the light pollution map of USA: as a proposal where to find the dark sky ( Sky Finder).
The British local astronomers' organization created a map of star-gazing places:
There are also some individual initiatives, developing web applications for the ones searching for a dark sky: like interactive map available online and an iphone app:
Above all, there are professional astronomers, working on An Artificial Night Sky Darkness Atlas. Already a decade ago, a paper with the whole world map and map extracts was published by Italians and Americans. The creation of map was based on "radiance-calibrated high-resolution DMSP satellite data and on accurate modelling of light propagation in the atmosphere". Apparently the Center of Europe, Japan and the Eastern part of United States of America are 'enlighten' artificially at most, where the natural night sky "is more seriously endangered than commonly believed"(

In order to protect the observatories from the light, to keep the night sky as dark as possible, the dark sky parks called dark-sky preserve are created. It started since 1999 and officially now there are a couple of decades. Mostly in USA and Canda, there are also some in Europe. Recently one is about to be set in Germany "near a town called Gülpe, some 120 kilometers west of Berlin" as tells. Interestingly, there is no map yet, marking those established parks.

But there are other mapping projects, as of, that every year asks public to participate in measuring their night sky brightness and submitting their results with a coordinates. It is used to raise awareness, and even WIRED is participating in spreading the message (
After submitted results, the Globeatnight prepares the data and provides the map to analyze the results ourselves:

It shows the magnitude the observer chose looking at the Orion Constellation, where the higher the magnitude the better, so the darker colour represents the clearer sky at the observation time.
One can observe the same data interactively, as well as all the data is freely available for download in various formats (and from various years) :

It would be interesting to somehow check the data or at least verify how much does it correlate with our urbanization pattern or at least street networks! Hope to figure that out!

Meanwhile, keep on searching for darkness!

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