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July 09, 2008
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
- 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
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!