Did you know that

Light pollution was already a problem for astronomers in the 19th century?
“It is evident that the city, in which the Observatory is located, is rapidly growing in every direction: coal smoke leaves the atmosphere more and more opaque, and the abuse of electric lights takes away most of the darkness of the night.“
With these words, written in a chronicle of the Brera Astronomical Observatory in 1893, Schiaparelli described the observational difficulties that he encountered when observing from Brera, due to deteriorating air quality and increasing light pollution. And it could only get worse in the following decades. Deteriorating environmental conditions at the Brera Observatory were instrumental in a search for a new and better observing site. Furthermore, the new method of research based on spectroscopy, that was rapidly becoming relevant for astronomers, required new telescopes and new instrumentation. In the 1920s, the Brera Director Emilio Bianchi acquired a villa and adjacent park in Merate, a town near Lecco, which would become the new observing site of the Observatory. The new telescope (a Zeiss reflector, 102 cm in diameter), and its spectrometer, was soon followed by other telescopes and new instrumentation, including the 49 cm Merz-Repsold telescope used by Schiaparelli in Brera (currently on display at the National Museum of Science and technology in Milano). The good quality of the site for astronomical observations lasted only a few decades: by the 1960s, the urbanization in the region caused poor observing conditions for the instruments in Merate. The situation escalated during the summer of 1990, when a nightclub in the town of Calusco d’Adda, just a few miles from the Observatory, turned on a rotating beacon that made all astronomical observations impossible. After a long legal battle, in which the Observatory could demonstrate beyond any doubt the damages caused by the beacon, the nightclub had to turn off the offending light. Light pollution is a very much debated topic, so far poorly regulated. In Lombardy, the Astronomers of the Brera Observatory have been instrumental in promoting a law, “Urgent measures to conserve energy in outdoor lighting and to contrast light pollution” that was approved on the 27th of March 2000 (Legge Regionale N. 17 del 27 Marzo 2000).
Light pollution is not only a problem for astronomers, for whom locating proper observing sites is becoming more and more complicated and the sites themselves are located in very remote places and difficult to reach. Too much artificial light at night is a stress factor for many animals, particularly nocturnal ones, and also for plants and humans. But this is another story!
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