Lights in Phoenix are in the process of changing to LEDs. A public comment period ended on June 30 that gave residents the chance to weigh in on whether a 4000 Kelvin bulb or a 3000 Kelvin bulb would illuminate better and be cost and energy effective. The respondents split almost down the middle.

To get a couple of perspectives, we spoke with Mark Hartman, chief sustainability officer for the city of Phoenix; and John Barentine, program manager of the International Dark Skies Association.

Hartman said the current lights are multi-directional and shine down on houses and the surrounding area. The new lights will be directed more precisely on the sidewalk and street. He said the 4000 Kelvin bulb is more comparable to moonlight and the 3000 Kelvin bulb is more yellow.

"There could a great win-win that certainly has the least amount of blue and at the same time is very cost-effective," Hartman said.

Barentine said the International Dark Skies Association is not opposed to LED lighting.  He advised the city research the lighting options because some places have updated lights only to get complaints from residents about the lighting being too sterile or hospital-like. 

"We're not necessarily going to come back to a point where you can see the Milky Way from downtown Phoenix," Barentine said. "But at the same time, I don't think the right thing to do is to simply accept that living in a heavily light- polluted environment...is a natural consequence of living in a city."

EDITOR'S NOTE: The City is deciding between at 4000 and 3000 Kelvin bulbs.