Three-quarters of major observatories suffer from light pollution

(ORDO NEWS) — Researchers from Italy, Chile and Galicia have studied and compared levels of light pollution at major astronomical observatories around the world.

The study shows that light pollutes the skies above most observatories and immediate action is needed to reduce the amount of pollution coming from artificial lighting.

The study presents light pollution levels at nearly 50 observatories around the world, including the world’s largest professional observatories as well as smaller amateur observatories.

In addition to studying the brightness at the zenith, the scientists used additional indicators of light pollution, which showed that the night sky at the main sites of the observatories is more polluted than you might think.

Additional indicators were the average brightness at a height of 30° above the horizon, the average brightness in the first 10° above the horizon, the total average brightness over the sky, and the illumination of the earth by artificial light emanating from the night sky.

The results of the study show that only 7 out of 28 large astronomical observatories (sites with a telescope with a diameter of 3 meters or more) have zenithal sky brightness with light pollution below the expected threshold of 1% of the natural sky brightness.

The smallest pointing direction for ground-based telescopes is about 30° above the horizon. Only one large observatory out of 28 has light pollution in this direction below 1%.

The 10% limit was set by the International Astronomical Union in the 1970s as the maximum allowed artificial brightness for large observatories.

A new study shows that light pollution at two-thirds of the ground-based observatories participating in the study has now exceeded this threshold.

Study leader Dr. Fabio Falchi said: “The least polluted of all the study sites is a house in Namibia, which houses several telescopes that are rented by amateurs for visual, photographic and research purposes.

I was there recently and can confirm that it is the least light polluted place I have ever seen. We must try to reduce light pollution at other sites to protect the future of ground-based astronomy.”

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