Tucson, which has long prided itself on its commitment to the containment of light pollution, is falling behind on that count as other cities join in the international movement to encourage darker skies and an better appreciation of the stars at night.
Flagstaff, in fact, does it better and has been burnishing its own long-established reputation for keeping its skies dsrk. While Tucson has been losing ground (or sky) in standards set by the International Dark Sky Association for better management of nightime artificial light, Flagstaff holds the distinction, which it won in 2001, of being the only certified “International Dark Sky Place” in all of Arizona, and is one of only five recognized dark sky communities in the world – the others are Borrego Springs, Calif.; Homer Glenn, Ill.; Isle of Coll in Scotland and Isle of Sark in the Channel Islands UK.
According to Barentine, the IDA’s goal is not just recognizing dark areas around the world; it’s also about the efforts taken by members of those communities to keep their skies dark through controlling the light pollution. Most communities designated by the IDA as official dark sky places are small, where it’s easier to come up with regulations that everyone agrees to.
Carmen Austin, secretary of the astronomy club at the University of Arizona, also does not think it’s going to get darker in Tucson any time soon.
“Not everybody cares about it,” Austin said. “There are people who are fighting against dark skies, and advertisers and businesses want to be able to have their big billboards really bright that really get people’s attention. They don’t care about if astronomers can do their thing or not.”
The city is still taking steps to reduce Tucson’s sky glow, though. such as the use of yellow street lights aiming downward, so that the light isn’t spiraling out into the sky itself. The color yellow has a wavelength that can be more easily overlooked by stargazing professional and amateur astronomers.
Observers from Kitt Peak National Observatory have watched the light in the skies over Tucson increase over the decades since Kitt Peak opened in the early 1960s. Astronomers can use old constellation maps to determine the level of light pollution in the sky, by comparing what used to be seen in the old maps to what actually can be seen today.
Austin also mentioned the effects of light pollution on wildlife, and studies that show how it might affect the health of some humans.
People who work nights are more likely to health problems in general, said Austin. “It’s not necessarily light-pollution related, but its showing that eventually if it’s not dark enough at night, or you don’t sleep in a dark enough place you are more susceptible” even to diseases like cancer, he said.
The outdoor lighting controls that Barentine spoke of are accessible on the Pima County website, and there were some major changes in February 2012, to the wording of the code.
The most important change in the code was to introduce color-spectrum limitation for both general lighting and signs. Lighting was limited 3,500 degrees kelvin and for signs 4,400 kelvin. This is considered a victory for dark sky enthusiasts, and yet prior code editions encouraged the use of low pressure sodium lighting which only emits 1,700 degrees kelvin.
Matt Root, a lighting engineer at IDA Tucson, said he didn’t understand why the color temperature limitation for signs was so high. He said signs are perfectly visible at 3,500k same as general lighting.
This increase in lighting temperature was allowed for a simple reason. Tucson’s dark sky is in competition with the impulse to shine bright light for commercial reasons. “Towns like Tucson in the western U.S.A. are ritually in a situation where they have to balance needs of economic development and growth against environmental protections. And we consider dark skies to be an environmental issue because it’s something that’s impacted by human activity….My organization is here to combat the belief that economic concerns come before environmental concerns,” Barentine said.
Flagstaff, on the other hand would not have met the IDA requirements for dark sky certification without help from its business community.
Professor Phil Mlsna, a member of the Flagstaff IDA, believes that Flagstaff got its certification by showing its long history of astronomy coupled with efforts of conservation that go all the way back to the 1950s.
“They had sweeping searchlights. It wasn’t in Flagstaff but in towns south of Flagstaff, I believe, where they were first noticed. You’ll often see searchlights at the opening of new stores, but when that was noticed near Flagstaff, astronomers thought that could be a problem, a beam of light sweeping around the sky making it difficult to make observations.”
The Lowell Observatory in Flagstaff and the Naval Observatory contacted the city manager and the council, and the Flagstaff business community, expressing their concerns. The city listened because the observatories had a close connection to the town. The extra dimension to the story is Percival Lowell, who helped found the Lowell Observatory, also happened to be both a businessman and astronomer.
The city then passed a law that even addressed light-pollution issues like commercial searchlights — the first such law anywhere, according to Mlsna. Chris Luginbuhl, another member of Flagstaff IDA, said that local business interests and those of the observatories located around Flagstaff are still intertwined and that is why there isn’t much opposition from businesses to dark sky ordnances.
Flagstaff’s lighting codes were first modified for darker skies in the 1980’s, when spectrum controls were added limiting the kinds of allowable outdoor lighting. Overall lighting that could be used in a developed area was also limited.
The two changes to the Flagstaff code were adopted in Tucson’s Outdoor Lighting Code in 2012.
Luginbuhl said that despite laws passed by both cities to keep their skies dark, violations resent in a civil suit at most. And the cities don’t have the resources to ensure wide community compliance.