Pittsburgh Goes Dark: Could This New Dark-Sky Ordinance Begin a Trend? – Sky & Telescope

Can you see the Milky Way from your home? Diane Turnshek can, and she wants to Pittsburgh to see it, too.

“I would like to shrink the ring people have to drive outside of the city to see the Milky Way dependably,” she says. “It’s about a 40-minute drive at this point.”

Turnshek (Carnegie Mellon University) is a dark-sky expert who helped draft Pittsburgh City Council’s new Dark Sky Ordinance, which covers the city’s parks, facilities, and all streetlights. With the new ordinance, the “ring” could be about to shorten dramatically. The new ordinance, which applies only to city-owned property for now, would replace 35,000 old high-pressure sodium streetlights over the next 18 months to two years. All will be dark-sky-friendly, with cut-off fixtures that direct light where it needs to go.

Crucially, the ordinance also replaces newer LED streetlights, the kind that were hastily installed in cities across the world in the 2010s. “About a decade ago, 4,297 streetlights were replaced with 5,000-kelvin LEDs,” says Turnshek. These bright, blue-white lights turn night into day, and are a leading cause of the world’s growing light pollution, so Pittsburgh will replace them with lower-temperature, amber-colored LEDs.

Pittsburgh City Council claims the new streetlights will “provide long-term savings and reduce energy usage and light pollution.” The new plans also include between 3,000 and 15,000 new LED streetlights found to be necessary during the analysis. Crucially, these will also all be dark sky-friendly: motion-sensored, shielded, and with both a lower wattage and cooler temperature.

Exactly what will be used remains to be seen; Turnshek is still in conversation with Pittsburgh City Council about controlling the  2,200-kelvin streetlights. “Dimming is essential, she says. “The lights shouldn’t run at full brightness … They understand that the total lumens output should be reduced.” She says many cities have made the mistake of picking low color temperature lights, but then putting them in way too bright. 

Part of Turnshek and others’ preparatory work included the monumental task of making a nighttime map of Pittsburgh’s 58 square miles. That was done using photos from drones taken only on clear, snowless, dry, and moonless winter nights — a painstaking task. The team also used a Sony DSLR camera under a Cessna aircraft as well as photos taken by astronauts on the International Space Station.

Is this the beginning of the end for cheap blue LED lights used in public lighting? “It’s too soon to tell,” says John Barentine (now at Dark Sky Consulting), who was peripherally involved in the effort while employed at the International Dark-sky Association. “I think that has been in motion for a while now, and it has been driven by a combination of public rejection of those bluer LEDs in favor of warmer lights, and generally better affordability of those warmer LEDs.”

Amateurs will be heartened to hear that dark-sky-friendly lighting has become more competitive with systems with higher color temperatures. Darker skies no longer come at a premium.

Of course, Pittsburgh’s ordinance isn’t specifically related to the needs of amateur astronomers. Its stated aims are to improve safety and security, reduce light pollution, save energy, and advance equity in all Pittsburgh neighborhoods.

However, it may also be a sign of an increasing interest in, and appreciation of the value of, dark skies. “There is a groundswell, built of people who feel deprived of a natural right to starlight,” says Turnshek. “Some young, who feel they were not given a choice, and some old, who remember the comforting beauty of the dark night sky as if it were yesterday.”

Turnshek began her mission to bring dark skies back to Pittsburgh with a 2015 TEDxPittsburgh talk called “De-Light The Night.” But Pittsburgh is not alone in its adoption of a dark-sky ordinance — nor is it the standard-bearer.

“The new Pittsburgh ordinance is not quite as restrictive as Flagstaff or even Tucson,” says Barentine. “But for major U.S. cities, especially those on the East Coast, it is quite a bit better than others that are out there — I think this is the future of outdoor lighting policy in the U.S.”

There is as yet no designation as a “Dark Sky City,” but Pittsburgh could soon be in a position to apply to the International Dark-sky Association to become an “International Dark Sky Community.” Either way, the new ordinance in Pittsburgh puts it ahead of almost every other U.S. city when it comes to dark skies.

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