The searchlights over the Benjamin Franklin Parkway have gone dark. The three-week Open Air show by Montreal artist Rafael Lozano-Hemmer is packing up.
But the issue of light pollution that simmered throughout is still with us.
It is of concern not only to astronomers, but to others who feel the bejeweled dark sky is an important part of living on Earth and being human. The lofty realm has inspired us to write poetry, compose music, ponder the existence of God, and fall in love.
But the ever-creeping glow of light into ever more remote spots has been dramatic. Drivers encounter "glare bombs" from service stations, car dealers, and parking lots. "Light pillars" shoot skyward from our cities. Streetlights once thought to enhance our safety and make our neighborhoods look friendly are now referred to as "pollution on a stick."
Drive any highway in the wee hours - as I did not long ago - and many spots are lit like Hollywood studio sets. How many of us can still see the Milky Way?
The push for energy efficiency may not have helped. True, some of the newer technologies can direct the light more precisely and require less wattage. Then again, some people who buy more efficient bulbs simply leave them on all night.
In 2010, researchers from the Sandia National Laboratories in New Mexico studied lighting use through history and found that humans have consistently favored more light as the technology progressed from candles to oil lamps to gas lamps to electricity.
The International Dark-Sky Association estimates that wasted lighting - misdirected or too bright, for instance - costs the nation $2.2 billion a year.
The effects of all this excess light are far-reaching.
Scientists have found that bright illumination can disorient birds - although in the case of Open Air, which coincided with the peak of fall migration, fears of birds getting "trapped" in the bright beams and becoming exhausted or slamming into buildings were largely unrealized.
Audubon officials credited the artist's tweaks to the show - changing the quality of the light and incorporating blackout periods - with lessening the risk to the birds.
Near beaches, excess light confuses newly hatched sea turtles who normally use the moon and stars to find their way to the ocean.
In June, the American Medical Association released a report on adverse health effects. It cited "potential carcinogenic effects related to melatonin suppression, especially breast cancer."
Other diseases that may be exacerbated by lighting's disruption of circadian rhythms "include obesity, diabetes, depression and mood disorders, and reproductive problems," the report said.
Excess lighting also causes air pollution, and not just from the increased power-plant emissions. National Oceanic and Atmospheric Administration researchers found that excess light at night can hinder chemical reactions that normally would reduce the amount of smog-forming chemicals in the atmosphere.
Perhaps not surprisingly, movements have been growing to take back the night.
The National Park Service has a "dark sky team" that has helped officials at dozens of national parks determine how much excess light they're shining into the sky, how much they're spending on it, and what they can do about it.
At Big Bend National Park in Texas, the team's recommendations cut lighting expenses 98 percent, said spokesman Jeffrey Olson.
He said national park officials, who contend that once the sun goes down you've seen only half the park, are seeing increased interest in the night sky. Many now hold regular stargazing parties.
As shining as Olson's assessment is, officials here are not as sanguine about progress.
Stan Stubbe, a northern Chester County resident and president of the Pennsylvania Outdoor Lighting Council, an advocacy group, remains dismayed by the growing nighttime glow in the region.
"Why the all-night lighting? It wastes energy and money, annoys the neighbors, and pollutes the night sky and natural environment," he said.
For 17 years, his group has worked with municipalities on ordinances to curb excess light. So far, at least 41 have taken such steps.
"For some, those issues loom large," Stubbe said. "For others they are meaningless. . . . We've made inroads, but there's no groundswell."
In August, the group designated a 73,000-acre swath of forest - the last large unbroken forest left in Southeastern Pennsylvania - as its first "night skies conservation area." The area, known as Hopewell Big Woods, includes French Creek State Park in northern Chester County and areas beyond.
Stubbe said that the Ches-Mont Astronomical Society, which holds star parties in the Woods, has been measuring the ever-brightening light. But to him, the inundation of light is already obvious - particularly from several shopping centers. "They're all pumping photons into the sky."
The council did a survey of the Woods and identified some of the major polluters it hopes to work with, including a church and a car dealership. The council also plans to work with homeowners.
That's where you come in.
Various groups, from Audubon to astronomy organizations, list steps regular people can take to reduce their "light trespass." Here's a sampling:
Turn lights off when they are not needed. This applies especially to decorative and landscape lighting.
Install motion sensors. Or timers that automatically shut off lighting at a set hour.
Use low-voltage or solar lights for some applications, such as outdoor walkways.
Replace high-wattage bulbs with a lower wattage.
Aim floodlights down or buy inexpensive shields.
Use LED bulbs, bird groups advise, because they are less attractive to birds than conventional halogen.
Ask local officials to minimize lighting in stadiums, at ball fields, playgrounds, and other public sites.
In June, PBS aired an award-winning film about light pollution, The City Dark. (See www.thecitydark.com)
Two citizen science projects are tracking light pollution. Check www.GlobeAtNight.org and the Great World Wide Star Count, which began Oct. 5 and lasts through Friday, at www.windows2universe.org/citizen_science/starcount/
"GreenSpace" appears every other week, alternating with Art Carey's "Well Being" column. Contact staff writer Sandy Bauers at 215-854-5147 or firstname.lastname@example.org, or follow on Twitter @sbauers. Visit her blog at www.philly.com/greenspace.