Photo: National Park Service composite of 47 images

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“The National Park Service captured the images showing the night sky and light pollution in Chelan County. To create a full picture of the night sky, NPS stitched together 47 different photographs, a process that can leave seams between individual image, some of which are visible in the images in the story… Evening sounds are from the Natural Sounds and Night Skies Division at the National Park Service. Solutions for reducing light pollution are from the National Park Service. LED lights are meant to save energy. They’re creating glaring problems.”

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“As societies developed, stars became less visible on the horizon. In one county in Washington state, the clarity of the night sky was marred by lights radiating upward and obscuring the view. This light pollution would only grow worse…

An unexpected increase in pollution came after Chelan County shifted to LED streetlights, which shine brightly while using less energy than traditional bulbs. One year after the change began, the additional glare masked about half of the previously visible stars. What happened there is not unique.

In recent years, cities, towns and small communities across the world have taken part in a radical revolution — of our lightbulbs. Traditional orange-tinged high-pressure sodium bulbs are being swapped for more energy-efficient, whiter and brighter LED (light-emitting diode) lights. But the rise of LEDs is also illuminating new problems for our night sky, as well as our health.

Over the past decade, scientists found, the night sky has become nearly 10 percent brighter each year because of artificial lights, mainly LEDs emitting too much glare. Streetlights are part of the problem, as are sources such as illuminated billboards and stadium lights…

‘People need to understand LED lights are being installed everywhere, not just streetlights, but they’re blasting up in all directions,’ said Jim White, senior energy efficiency engineer with the Chelan County Public Utility District who helped with the county’s LED transition…

Researchers with the National Park Service found the LED lights washed out more of the stars, particularly near the horizon.

‘You can tell the lighting gets bigger, so it extends higher into the sky … the entire sky got brighter,’ said Li-Wei Hung, an astronomer with the National Park Service who published a study on the LED transition in Chelan County. ‘Just a few years ago, this [was] really new knowledge for us. Does the change to LEDs really decrease the light pollution or increase it? We [didn’t] exactly know.’

Camera data showed the sky over local Burch Mountain was 60 percent brighter after the county completed the switch in 2019 compared with 2018.

The new artificial light stood at 3.69 times the natural light level after the transition; before the transition, artificial lights generated 2.30 times the natural light. White said the increased pollution was ‘a total surprise’ because the Public Utility District had tried to direct lights toward the ground, but the light still scattered.

Detailed nightglow data from individual cities is hard to come by, making the transition in Chelan County an important case study in understanding both the good and bad effects of LED lights. Yet observations and anecdotes indicate Chelan County is not alone. From 2011 to 2022, reports from citizen scientists indicated the average night sky got brighter by 9.6 percent each year, which researchers attribute to LED light replacements. Some cities, such as D.C., paused a transition to LEDs after residents complained about the bright lights disrupting their sleep…”

— Kasha Patel, Kati Perry, Daniel Wolfe and Emily Sabens, Washington Post

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