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Last Updated:
July 09, 2008



Onan Observatory

Light Pollution 101

Metro-area light pollution map, assembled by MAS member Craig Cotner, shows the extent of the problem.  Pink areas are heavily light-polluted with incrementally less pollution indicated by yellow, green and purple.  Note the encroachment of the Twin Cities' light pollution on the area around the Onan Observatory. 

What is light pollution?

An unfortunate side affect of growth and development is increased levels of "light pollution" -- light which doesn't serve its intended purpose of providing safety and convenience. Instead, it spills outward and upward from poorly designed or inefficient light fixtures, trespassing on surrounding properties and polluting the skies. 

"Light pollution" includes:

  • Urban sky glow: the single greatest threat to mankind's view of the universe
  • Glare: blinds us and affects our ability to see into shadowed areas, often defeating the original intent of "security" lighting
  • Light trespass: when someone's outdoor lighting affects us in an unwanted way, "trespassing" on our property
  • Clutter: confusing, conflicting lighting, particularly affecting automobile drivers
  • Energy waste: over one billion dollars a year is wasted in the U.S.A alone because of ineffective or inefficient lighting

The results? The stars are much more difficult to see. Children and adults no longer understand nor appreciate the impact and importance they once had for our ancestors. And in many Minnesota cities and towns, children are growing up who may never appreciate the natural beauty of the Milky Way on a warm summer night, or may not be able to enjoy the next "big comet" when it someday appears. 

The Minnesota Astronomical Society is committed to bring people of all ages out under night-time skies to recapture the awe and joy they once held for everyone. To achieve this goal we educate people on the impacts of poor and inefficient lighting and encourage cooperation and improved planning regarding outdoor lighting.

The Society is also working to achieve our goal in a much more tangible way -- by operating a publicly accessible observatory at Baylor Regional Park in Carver county. Take a quick look at the skies above you and at the surrounding horizon and you'll easily see how light pollution, if left un-checked, will impact the long-term viability and benefit of such a valuable public asset.

What can you do about light pollution? 

Insist on quality lighting and use it yourself. Quality lighting is well shielded (so the light is used, not wasted), uses the right amount of light, includes time controls when possible and includes the use of low pressure sodium (LPS) as the light source when possible (LPS is the most cost effective light source, excellent where color rendering is not critical). Such quality lighting is directed downward where it is needed, not up or sideways where it is wasted and causes glare, light trespass and bright skies.

Working together we can improve the quality of the night-time skies over Minnesota without sacrificing the safety, security and convenience of outdoor lighting!


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