Dark-sky Threats: Gwilym, Crossroads continue the battle against light pollution

Tom Gwilym and the Door Peninsula Astronomical Society (DPAS) won a major victory to protect the dark sky near their observatory in 2021. But their efforts to “keep the Door dark” at night have not stopped at Gwilym persuading a billboard company to turn off a light that shone straight up into the sky in Sevastopol Township between the Sturgeon Bay city limits and the dark-sky-designated Highway 42/57 scenic byway. His work and advocacy have earned him a title and duties as the international dark-sky advocate for northern Wisconsin.

During a Keeping the Door Dark program this month on the DPAS property east of Sturgeon Bay, DPAS president David Lenius said the society still has difficulties getting clear views of the night sky and targets near the horizon because of light pollution from a business to the north , from light glow over Algoma and especially from Sturgeon Bay to the west and southwest.

“The Sturgeon Bay Nebula,” Lenius said, citing a nickname that DPAS members have for the glow to the west of the observatory and telescope. Lenius said the astronomical society site east of Crossroads at Big Creek used to be “in the middle of nowhere ,” but light from the city has gotten nearer and nearer in recent years.

Gwilym emphasized that DPAS needs to keep persuading governments, private-property owners and business owners to use lights that shine only when and where they’re needed. He showed nighttime drone photos of lights shining upward and outward and off the “gas station and popular hamburger restaurant” property at Highway 42/57 and Gordon Road. He wants that site to change its lights to shine downward so they stop interfering with the observatory’s view.

Gwilym said DPAS is working for all of Door County to improve and limit its lighting so that Newport State Park can maintain its status as an International Dark-Sky Park. Increased lighting in Sister Bay poses a threat to the dark sky throughout Northern Door and at Newport, which was Wisconsin’s first site to receive the Dark-Sky Park designation.


In addition to showing the audience – 20 people indoors and 36 on Zoom – examples of bad lighting, Gwilym put up a chart of side-by-side options for good lighting for homeowners.

One example showed a farmyard and cylindrical barn lights that not only wash the ground and barn with light, but also “spray light everywhere,” including up into the night sky. Instead, he advocated putting those light fixtures – or smart bulbs – on motion sensors and adding a shade or replacing them with lights with shades to minimize the outward spread.

Gwilym also presented a slide of empty streets in downtown Sturgeon Bay completely lit up, with rounded city street lights shining upward into the sky and outward toward second-story apartments.

He and DPAS are watching from the sky as well. He showed drone photos that proved how many sites have lights glaring up into the sky.

In addition to sharing the examples of what not to do, he shared what he thought were good practices, such as installing lights that shine straight downward at the 42/57 roundabouts, and an aerial photo of Pick ‘n Save grocery store lights that do not shine up and instead, perfectly light only the rectangular outline of the store property and parking lot.

Gwilym also presented photos of the new Fincantieri Bay Shipbuilding site that was constructed for government contract work and noted that light washes downward, not upward on that building. He said the lighting’s good there, but at the rest of the plant, “not so much .”

In addition, Gwilym has been writing letters to new-business developers, urging them to use dark-sky-friendly lighting. He said Kwik Trip’s corporate office sent him specifications for the light fixtures as well as the placement of lights planned for the new convenience store and gas station planned on Egg Harbor Road within two miles of the observatory.

The International Dark-Sky Association provided a chart of dark-sky-friendly alternative lighting.

Lenius said almost all homeowners – himself included – have a light or two that pollutes the night sky or spoils the homeowner’s own view of the stars and Milky Way. Instead of changing out the entire fixture, he suggested adding a shade, putting it on a timer or adding a motion sensor so that it shines only when needed. Neither should homeowners believe that energy-saving LED lights mean they can light up their yards or their neighbors’ yards, or simply leave their porch light on all night.

“At my house, I have these horrible LEDs that light up,” Gwilym said. “I’m a little bit guilty, but I have it on a four-minute timer.”

People should choose LED bulbs that are 3,000 Kelvin or less and avoid cool, blue-rich types of lights. Gwilym said there are ongoing studies about the adverse effects of blue light during the night and, conversely, the benefits of bluer light during the daytime hours.

While he’s been out front battling for Door County’s dark skies, he’s by no means alone in Wisconsin and worldwide. For years, the International Astronomical Union has fought light pollution from the ground, and this winter, the organization opened a new campaign to limit light and radio interference from big satellite networks.

With the number of satellites in orbit predicted to reach 100,000, the group urges companies to use less-reflective materials on satellites and avoid radio frequencies used by astronomers. Gwilym’s Keeping the Door Dark program took place during the same week when 47 more satellites launched, and he said he could do an entire hour-long program on how satellites interfere with photography and observatories.

He also said light pollution adversely affects wildlife, plants, bird migrations (such as birds running into buildings in cities) and humans’ circadian rhythms. Gwilym showed a photo of a maple tree that did not drop its leaves on the side that always received light from a spotlight. The DPAS neighbors at Crossroads at Big Creek, including Coggin Heeringa, frequently point out the benefits of dark skies in nature. She’s noted that light pollution can adversely affect insect behavior and that, in turn, can threaten bird species that rely on those insects as food.

Gwilym gave one example of adverse effects on amphibians, noting that sea turtles normally hatch and turn toward the ocean because of the reflection of light on waves. Often, those that hatch in cities turn toward artificial light and die inland or get smashed by cars.

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