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Eyes on Night Skies

Babbitt Ranches is believed to have some of the darkest skies in Northern Arizona and soon, scientists expect to have the data to prove it. Astronomer and Northern Arizona University Campus Observatory Director Ed Anderson says preliminary measurements taken at four locations on the ranches – north of Wupatki National Monument, near SP Crater off Highway 89, north of Cedar Ranch camp and near Tin House ranch camp north of the San Francisco Peaks – all reveal extraordinary dark sky quality.

“We’re at ‘excellent’ for all four sites,” he said.

Anderson and Babbitt Ranches President and General Manager Billy Cordasco gathered data in December using a new night sky brightness monitoring system for a project called Eyes on Night Skies (EONS), developed by Dark Sky Partners, LLC, of Flagstaff. The EONS project is designed to address the increasing concern of man-made light in the night sky around the world.

“The EONS project uses light meters similar to exposure meters photographers may have pointed at their subjects years ago,” said astronomer Chris Luginbuhl of Dark Sky Partners. “It points straight up and senses the light that comes from a portion of the sky overhead. It’s not able to distinguish light pollution from starlight and moonlight, but you can determine the natural conditions by knowing the characteristics of the location and by studying how it changes over time. For example, when the Milky Way passes overhead, the measurement goes up.”

Astronomers use a measurement scale where larger numbers correspond to lower or fainter brightness. The International Dark-Sky Association (IDA) rates the quality of starry nights for locations considered for dark sky recognition. “For Dark Sky Reserve status, the numbers at various locations have to be greater than 20. Anything less than 20 is too bright,” said Anderson. “A city sky is less than 18. A bright suburban sky might be 19. A rural sky is nominally about 21. A truly dark site is darker than 21.5. Our preliminary data shows Babbitt Ranches at 21.6.”

Babbitt Ranches is bordered by locations that have received IDA dark sky designations. Flagstaff is the first International Dark Sky City; Flagstaff Area National Monuments – including Sunset Crater Volcano, Walnut Canyon and Wupatki – and Grand Canyon National Park are all recognized IDA International Dark Sky Parks.

In an effort to measure and monitor Northern Arizona’s darkness over time, Babbitt Ranches will be working with Dark Sky Partners and installing battery-operated EONS stations, which will each collect data every five minutes every night, or almost 100,000 measurements every year. NAU, Lowell Observatory and U.S. Geological Survey also are participating in the EONS project. Luginbuhl plans to have seven of the sophisticated light meters operating around the Flagstaff area by the end of 2021.

“We’re looking for long-term trends and how the sky is changing with growth,” said Luginbuhl. “Measurements from nearly pristine areas like Babbitt Ranches and from locations with well-controlled lighting like Flagstaff contribute a lot to the understanding of light pollution and natural variations.”

“Along with the Babbitt Ranches community, we’re thrilled to participate with the EONS project in the collection of information to learn and understand more about our dark skies in Northern Arizona, as well as be thinking forward as to how to maintain and conserve these beautiful night skies for future generations,” said Cordasco.

Luginbuhl and Dark Sky Partners will analyze the EONS data from Babbitt Ranches and elsewhere. FBN

By Bonnie Stevens, FBN

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