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Dark Sky

When was the last time you saw the stars at night? I mean, really saw them, from the constellations of the zodiac low on the horizon to the north star? Was it the last time you were out in the country far from any city? And do you remember, if you're of a certain age, how you could always see the stars on a clear night from where you lived when you were growing up?

Street lights on South Kings Highway

The reason that all but the very brightest stars have vanished is light pollution. Because of the increased population densities and concerns about safety for drivers and security for businesses and neighborhoods, over the years we've installed more, and more powerful, street lights, security lights, lights on businesses, and lights on public facilities. Because most of this lighting was poorly designed, it directed more light out and up than it directed down. That light went into the sky and, often, into the neighbors' windows and eyes. The result is a night sky where the horizon is a permanent orange glow, the night is just a somewhat dimmer version of day, and you have to shut your shades to keep the outside lights out of your eyes.

Besides its destroying the ambience of the night, ruining drivers' and pedestrians' night vision, making life miserable for astronomers and Boy and Girl Scouts, and confusing nocturnal wildlife, is there any reason to care about light pollution? There's one big one. All that light that's being wasted costs money to produce, but creates no value in return. If we can direct and reflect downward all the light an outdoor fixture creates, we can use lower wattage bulbs in those fixtures, often reducing energy consumption by half. That's money saved for the taxpayers and a reduction of the effects of electricity production on the environment.

The Solution

Properly designed lighting, often called full-cutoff, shields the lamp on the top and sides and uses reflectors to reflect all the light down in the desired pattern. To the right is a photo of the parking lot at Edison High School where new lighting fixtures direct the light downward. The parking lots at Hayfield Secondary School are similar.

Three lights at the Edison front parking lot

The bad news is that street lights are a huge contributor to light pollution. The first image on this page shows a scene on South Kings Highway. The street light closest to the camera uses a newer fixture and the next street light uses the older "cobra head." There's not a lot of difference in the two. The good news is that much better fixtures are available (as the parking lot photo illustrates) and aren't expensive. A lighting manufacturer estimated that a very good fixture should cost about $150 and perhaps another $100 to install. A local jurisdiction could accelerate the schedule for replacing street lighting for not a lot of money. And homeowners who wanted to replace the street light outside their house could pay a reasonable amount of money to their local government to do so.

What About Security?

It's absolutely true that people feel more secure the more artificial lighting there is at night. However, the limited number of studies done don't prove that people actually are more secure. First, harsh, poorly designed lighting creates shadows in which predators can hide. The brighter the light, the better the cover a shadow provides. Second, security really depends on the presence of other people to keep predators away. The bottom line is that you're most safe at night in an evenly lit place where there are lots of other people around. Glare going into the night sky contributes nothing at all to security.

Sports Field Lighting

Some of the most important lighting advances have come from lighting sports fields in public parks. Homeowners living near the fields are concerned about light spilling over onto their property and glare from the lights shining in their windows. And they don't care much for the night sky being lit up as if it were day. The good news is that properly designed full-cutoff fixtures can solve these problems, as the photos below show. (Photos courtesy of Soft Lighting Systems, the firm that provided the lighting).

Baseball fields lit by full-cutoff fixtures

Soccer/Baseball field lit by full-cutoff lighting

A key advantage of this lighting done well is that high balls (high flies, kickoffs, punts, etc.) aren't nearly as easy to lose in the lights.

Other Resources

Dark Sky Society

International Dark-Sky Association

Soft Lighting Systems, Inc.

Thanks to Del Armstrong, P.E. of Soft Lighting Systems for spending several hours trying to educate me about good outdoor lighting and walking around Lee District Park with me. Any mistakes on this page are mine alone.


This article can be found at
http://www.dougboulter.com/policy/darksky.html


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