CEDAR RAPIDS — Dark-sky advocates say the ongoing transition from less-efficient high-pressure sodium lights to brighter LEDs threatens to further illuminate night skies in urban areas to the detriment of natural aesthetics and the well-being of plants and animals.

Not so, say representatives of Iowa’s two leading utilities, Alliant Energy and MidAmerican Energy, both driving forces in the transition to light emitting diodes.

Terrence Cook of Iowa City, a night sky photographer and amateur astronomer, is in the dark-sky camp.

“The night sky is being lost to excessive light pollution in growing population centers,” he said.

The International Dark Sky Association defines light pollution as excessive and inappropriate artificial light whose main components include urban sky glow, light trespass, glare and clutter.

Speaking as a photographer, Cook said, “You lose a certain number of the stars to the glow, and you lose background depth when you photograph against a pale sky.”

Cook also worries that intense artificial light disrupts the light and dark rhythm that plants, animals and humans have encoded in their genes, with especially harmful effects on nocturnal creatures.

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One of the greatest detriments, according to Cook and other local astronomers, is the loss of opportunity to witness the natural brilliance of a star-studded dark night sky. Most young people today have never really had that experience, said University of Iowa astronomer Robert Mutel, who periodically conducts research in Arizona, where remote mountaintops remain suitable sites for powerful telescopes.

When he started teaching 30 years ago, Mutel said most of his students said they had seen the Milky Way, the galaxy containing earth, its solar system and a few hundred billion stars.

Nowadays, he said, just one in three students claims to have seen the Milky Way, whose profusion of celestial bodies appears as a faint cloudlike glow across the dome of a darkened sky.

“I certainly understand the concerns with the expansion of LED outdoor lighting,” said Doug Slauson, past president of the Cedar Amateur Astronomers, which jointly operates the Eastern Iowa Observatory and Learning Center at Palisades-Dows Preserve with the Linn County Conservation Board.

“Most Americans can’t imagine how stars appear in a truly dark sky,” said Slauson. He recounted an experience in western Nebraska where the stars were brilliant enough to cast a shadow of his arm against the hood of his car.

Though LED lights are often properly directed toward the ground, their brightness can cause excessive glare, particularly around reflective surfaces such as snow-covered ground, he said.

‘Missing out’

Brent Studer of Iowa City, who teaches astronomy at Kirkwood Community College, said the majority of his students have never seen the Milky Way, and he thinks they “are really missing out on something important.”

Studer said he believes LED light pollution can be managed with shields that aim the light directly down and with diodes that produce light on the warm side of the color temperature scale.

Higher color temperatures (4600 or more on the Kelvin scale) are called daylight colors and appear blue-white. Midrange color temperatures (3100K — 4600K) look cool white, while lower color temperatures (up to 3000K) are called warm white and range from red to yellowish-white in tone.

The LED lights used by both MidAmerican Energy and Alliant Energy on most of the streetlights in Iowa are in the 4000K color temperature range.

MidAmerican last August began upgrading more than 100,000 of its streetlights in Iowa, including 2,381 in Iowa City. Over the next 10 years, all Iowa cities in its service territory will be transitioned to LED as the existing streetlights fail, according to MidAmerican Energy spokeswoman Ashton Newman,

Alliant Energy, which operates hundreds of thousands streetlights in 600 Iowa and Wisconsin communities — including Cedar Rapids — is about half way through its transition to LED units, according to spokesman Justin Foss.

Both Foss and Newman said the new LED streetlights — designed to emit light directionally rather than spilling into the sky or nearby windows — actually pollute the sky less than the fixtures they are replacing.

Foss said Alliant’s replacement lights have been approved by the International Dark Sky Association.

Newman said MidAmerican knows of no professional studies that have validated adverse effects on circadian rhythms.

Foss said the LED lights last from 20 to 25 years, which compares with five to seven years for the high pressure sodium lights they are replacing.

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LED streetlights consume from 35 percent to 50 percent less energy than current streetlights, according to Newman, who said it will take from five to 10 years to recoup the replacement cost through energy savings.

Beside energy savings for the cities, the much longer life span of LED bulbs also will yield lower maintenance costs and fewer outages, both Newman and Foss said.

For MidAmerican, once the conversion is complete, the anticipated annual savings of 32 million kilowatt-hours of electricity will represent a reduction in carbon dioxide emissions of about 22,000 tons — the equivalent of sidelining 4,681 cars per year.