DULUTH – The Lake Superior Zoo had no problem gaining its certification as a Dark Sky business: the qualifications are similar to those required of a zoo housing nocturnal and crepuscular animals.

To get this recognition from Minnesota's chapter of Dark Sky International, a business' outdoor lights must have shields that keep light from shining upward. The glow can't shine onto streets or neighboring properties. The lights' color temperature ratings must be warm — 2700 Kelvins or lower. And all future lighting must be dark-skies friendly.

As a conservation organization, the zoo was an easy fit for distinction. In catering to birds, bats and cats that are active in the darkest hours, they already meet much of the criteria.

"We don't even have lights on at the zoo at night," said Caroline Routley, the zoo's marketing manager.

The more than 100-year-old zoo in western Duluth is one of several businesses to earn Starry Skies North's first round of certifications during a small ceremony at the zoo last week. It's a category dominated by local businessman Scott Vesterstein, a longtime advocate for cutting light pollution. He earned certification for Fitger's, The Village at Matterhorn, Capstone Apartments and Village Place Apartments. Another is contractor Randy Larson for Meteek Supply.

Other local groups include the Duluth Housing & Redevelopment Authority for Sky Ridge Flats, along with the Village at Matterhorn.

Jill Keppers, the authority's executive director, said lighting was an important feature and an early consideration when it came to the two new developments. Projects required more light posts, but installing a system that is dark skies-friendly was easy, she said.

"When I learned about wildlife-friendly lighting, it's something I felt strongly about," Keppers said.

The Dark Skies movement is an effort to dim light pollution with the goal of a more visible night sky. Advocates say visible night skies have benefits ranging from environmental to quality-of-life to increased astrotourism — travel to a destination for stargazing.

Northern Minnesota is rich in dark-sky spaces. The Boundary Waters Canoe Area Wilderness is a more-than-million-acre dark sky sanctuary, a distinction awarded by Dark Sky International, and is the largest of its kind in the world. Voyageurs National Park and Ontario's Quetico Provincial Park are also on the list.

Starry Skies North also has plans to award businesses in Grand Marais, Minn., including its new City Hall. Last week, mayors from International Falls, Ranier and Fort Frances and the Koochiching County Board recognized International Dark Sky Week.