Common Sense Solutions

Dark Sky Friendly Home Lighting Program — New!

Is your home nature, neighbor, and night sky friendly? Download an inventory form (below) and follow five simple steps to find out. The IDA created this new program to help homeowners and renters improve their lighting. Most people will find that a few simple changes can lead to home lighting that is both beautiful and functional, without contributing excessive light pollution.

“Five Principles of Responsible Outdoor Lighting” is a joint project of the
International Dark-Sky Association and Illuminating Engineering Society

4 Steps to Neighbor-friendly Montana Outdoor Lighting


The light source (filament, LED, etc.) should be recessed within the light fixture (“shielded”) so the light only shines down below the horizon where it is needed (not wasted up into the sky!) and does not trespass or illuminate the adjacent properties. Proper shielding minimizes the painful glare that temporarily blinds us when walking or driving at night.

Four common sense steps to better lighting and starry skies


Use warm-colored outdoor LEDs that are less than 3,000 Kelvin to protect human health and native wildlife. Cool ‘blue-white’ LEDs have been linked to breast cancer, colon cancer, obesity, depression and more, according to the American Medical Association. Cool LEDs also generate 2-5 times more sky glow pollution than warm-colored lights.


Use the appropriate amount of light that works best with human vision. Over-lighting constricts our pupils and decreases our ability to see safely at night! 


Only use outdoor lights WHEN and WHERE they are needed, and don’t waste money by leaving lights on all night. Use timers and motion sensors instead, especially here in Montana where we often have snow on the ground that can reflect 80% of the light up into the sky.

Examples of Light Pollution Solutions


In this shielding demonstration, light levels are read with and without a shield using a lux meter at the ceiling and on the floor. With the shield in place, light wasted into the sky is cut by 67% while usable light on the floor increases by 300%. The shield also eliminates almost all of the blinding glare and makes it safer and less painful to look towards the light fixture.


White LEDs above 3,000 Kelvin mimic daylight. When used at night, they suppress melatonin production and generate much more sky glow pollution than traditional sodium street lights. 


Several cities have experimented with different light levels for street lights (see ‘Dark Sky Library’). In almost every case, residents didn’t even notice when levels were lowered to 50%. And after midnight, some cities are now turning streetlights off to save money. At night, our eyes actually work better with lower light intensities than with super-bright lights that create blinding glare and deep shadows. 


Good lighting is very helpful when it’s in use. But leaving lights on full intensity all night when no one is around just wastes money and generates light pollution. Timers can automatically dim lights down or turn them off in the late evening. Motion sensors can turn lights on when there is activity and back off again when no one is in the area. This is extra important when there’s snow on the ground.

‘Good neighbor’ lighting uses all of these steps to prevent light trespass!