Sunday, January 8, 2023

Which sky has the least luminous pollution in the world?

Mountain peaks, islands or deserts: these remote places are the typical places where nowadays are the main astronomical observatories. 

For decades now, astronomers have been fleeing cities in search of skies without light pollution, which unfortunately are becoming increasingly rare.

A recent study has studied light pollution near the main astronomical observatories with telescopes with a diameter of more than 3 meters, drawing up the ranking of the best skies. Sadly, of the 28 sites considered, only seven have a sky that at its zenith is practically perfect. All other observers should consider light pollution problems.

The sites with the best sky are Cerro Paranal in Chile, where the VLT is located, and nearby Armazones, where ESO is building a 39-metre telescope that will become the largest in the world. Then follow other locations in Chile, both in the Andes and in the Atacama Desert.

Outside the South American state, observatories with the best sky are the South African Astronomical Observatory in South Africa and the Australian Astronomical Observatory in Australia. These are followed by the summit of Mauna Kea in Hawaii, and the Sierra de San Pedro Martir in Mexico.

The situation regarding Italy is bleak, as shown by the data for light pollution in the skies above the Astrophysical Observatory of Asiago, which houses the Copernicus, which with a diameter of 1.82 meters is the largest telescope on Italian soil. Despite some laws enacted by the Veneto Region to limit light pollution, the astronomers of Asiago have seen an inexorable worsening of the sky over the years, with an increase in lights on both the Plateau and the Po Valley. The authors of this study estimated that from the Asiago Observatory the average brightness of the sky at a height of 30 degrees above the horizon is 40% higher than the natural brightness of the sky.

Of all the sites studied by this study, the best sky is not located at an astronomical observatory, but in a very remote location in the Namibian desert. On this site there is a lodge with several telescopes that are rented to amateur astronomers for the period of time they stay. A true paradise for amateur astronomers where anyone can go!

Credit: ESO.

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