The artist, Rafael Lozano-Hemmer, who said his temporary installation literally pales in comparison to the outpouring of light from buildings, streetlights, and other urban sources, has invited discussion of the issue.
"I've reached out to the community a lot," he said.
On Oct. 2, from 8:30 to 9:30 p.m., he is giving the controls to Derrick Pitts, chief astronomer at the Franklin Institute, for a "Planetarium on the Parkway" star party.
In an e-mail to the region's astronomers, Pitts said light pollution in Philadelphia "is a train that left the station back in the early 1900s, and there is no return trip." He also said he thought it was more important "to focus efforts to improve lighting in areas where there's really a chance to make a difference."
But the debate has taken an ugly turn.
A Chicago woman who earns her living as a dog groomer, but who also is a dark-sky activist, has waded in, lobbing insults at the artist and at Pitts, both in e-mails and on the Facebook page of the International Dark Sky Association, an Arizona-based advocacy group.
On it, she called the show "the worst example of a public art display" and said of Lozano-Hemmer, "You do a great disservice to mankind."
Audrey Fischer has received a permit from the city to protest from noon to 11 p.m. Thursday and Friday at 20th Street and the Parkway.
Lozano-Hemmer kept it more or less friendly for a while. "I am happy you got your permit, Audrey, it speaks well of Philadelphia's openness," he wrote in a post.
But later he referred to "your belligerent world" and closed with, "Good luck, Audrey, sorry you could not find a more productive target for your activism."
Fischer said Wednesday that she did not know how many people would join her - other than one New York activist.
She said she would have educational displays and pictures of the night sky and, after dark, would set up telescopes.
"I just don't know how this is going to play out," she said. "All I know is I have to do what I believe in."
Lozano-Hemmer has designed a program interface that will allow Pitts to use the light beams as giant pointers to objects in the night sky.
Pitts said the art show presented "a teachable moment," and added, "I'm simply not going to fight with someone when there is an opportunity to teach."
Pitts plans to point out some of the main constellations and the brightest stars, such as Vega, which he said "looks more like a diamond than any other star."
"At the same time," he said, "I will also point out that it is extraordinarily important that we all do as much as we can to preserve our dark skies, wherever we can do that."
As part of the free party, astronomers from the Rittenhouse Astronomical Society, and perhaps other regional astronomy groups, will set up telescopes on the Parkway.
The party is a first, said Penny Balkin Bach, executive director of the Association for Public Art in Philadelphia, which is hosting the show.
She said she was "just very excited by all of the collaborations" and declined to discuss "the derogatory language."
Another first: The city will turn off streetlights along the Parkway during the show, which Bach said has not happened since they were installed 75 years ago.
Lozano-Hemmer said those streetlights, because of their proximity to passersby, produce 1,000 times the light pollution of "Open Air."
The astronomy community has largely avoided - at least publicly - making the dispute personal or saying whether a protest or a star party was the appropriate response to the light show.
P. Edward Murray, former president of the Bucks-Mont Astronomical Association, opposes the art project overall. Given the recession, "at the same time these 'artists' have secured funding to play 'flashlight tag' with high-powered searchlights? They should be ashamed," he wrote in an e-mail.
"It's about these horrible lights . . . and destroying the magnificent night sky," said Bob Gent, past board president of the International Dark Sky Association (IDA) and the Astronomical League, a nonprofit federation of astronomy societies.
Scott Kardell, managing director of the IDA, said the group "is certainly opposed to shining bright lights into the sky."
But, he said, "we're all adults here, and people have various things that are important to them, and a reasoned argument is a good way to go."
Lozano-Hemmer said he thought the name-calling was marginalizing an important issue and a concern he shared.
"My two cents: Audrey is hurting the dark-sky cause," he said, adding that he appreciated the work of others "who have the civility and the necessary diplomacy to stand up for this issue."
"It is true that my work is light-polluting," he said, but he pointed out that it was also ephemeral and temporary. "I would refuse to do a project such as this that is permanent," he said. Neither would he do the project in a spot that was not already suffused with light pollution.
"The majesty of a starry night," Lozano-Hemmer said, "cannot and should not ever be taken for granted."
As for the birders, they were worried because research has shown that birds could be disoriented by bright lights, essentially becoming trapped in the beams.
But Lozano-Hemmer has agreed to tweak the light quality and intensity and to interrupt the show briefly if ground-watchers reported bird problems to his technicians.
Audubon Pennsylvania's Janet Starwood said that, although funding was still needed, the organization has succeeded in getting radar sensitive enough to get a detailed look at bird movements and audio equipment that would help birders identify species by their flight calls.
Contact Sandy Bauers
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