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by Tim Hunter and Dave Crawford

The International Dark-Sky Association (IDA), Inc.



Most amateur astronomers are aware of light pollution and light trespass, and many amateurs are working hard to improve the night sky conditions in their communities. They often come across a variety of objections, which are usually based on inaccurate facts, misconceptions or, at times, deliberate falsehoods. Many of the objections to improving our night skies should be categorized as "lighting myths." Some of the more common and egregious myths are summarized below. Those who want to fight light pollution and light trespass should become particularly familiar with these myths and learn the actual facts behind them.


"The more light the better" is the same type of reasoning as saying the more salt on your food the better, or the more fertilizer the better, or the more medicine the better. Obviously, there comes a point where you can have too much of a good thing. Eventually, it becomes wasteful and harmful. Nighttime lighting behaves in the same way. We all need well lit main streets, security lights, and parking lot lighting. However, we do not need glare, clutter, confusion, light trespass, light pollution, and energy waste. Excessively bright, numerous, unshielded lights cause exactly these things.

You only need enough light to perform the task at hand. For example, you use low watt colored bulbs for Christmas tree lights, and a 100 watt bulb for a porch light. If more light were better, why are night lights in a bedroom dim instead of bright? The next time you are at an airport at night look at the brightness of the taxi lights (blue color) or the runway lights (white color). They are relatively dim so as to not harm the pilot's night vision and cause confusion. Even the rotating airport beacon is not especially bright. The strobe lights on tall chimneys and radio towers are of low wattage, yet visible for miles. Those who claim the more light the better often are salesmen or manufacturers more interested in sales than effective, safe, environmentally sound lighting.

The Illuminating Engineering Society of North America (IES or IESNA, 120 Wall Street, 17th Floor, New York, NY 10005) is the main professional organization for lighting engineers in this country. The IES publishes many information books for lighting professionals and has established sets of recommended lighting levels for various applications. For nighttime sports activities, these recommended levels may be quite high, but for security lighting in a rural area with little activity, they will be quite low. The IES recommended lighting levels are not the absolute answer for every lighting situation or need, but they are a good start for most occasions requiring a reasonable amount of nighttime lighting. In general, it is a good idea for a lighting application not to exceed IES recommendations, because this will usually lead to wasted energy and possible light pollution, light trespass, and glare.

The International Dark-Sky Association, Inc. (IDA) is a sustaining member of the IES and believes very strongly in the professional approach the IES takes toward lighting applications. Most of the individual members of the IES make their living designing indoor and outdoor lighting systems, and many of them are familiar with IDA. Most professional outdoor lighting engineers who are members of the IES are supportive of IDA's goals.


Light pollution affects all of us. It robs the professional astronomer of a livelihood and hinders the amateur's enjoyment of a hobby, but it deprives everybody of the awesome grandeur of the night sky. Many persons who claim this is of no importance have never gone far enough out of town to see what they are missing. Those who grow up in an urban environment may never see the Milky Way. How can someone miss something he or she has never seen?

The loss of the night sky desensitizes us to other insults upon the environment. It's the same as saying the loss of a virgin forest is of no concern, because most people don't live in the woods, and there are plenty of trees elsewhere. The loss of wild flowers, polar bears, wolves, whales, and other threatened species, to be honest, won't affect the average person. Their loss only directly impacts biologists who study them. After all, mankind has done very well without mammoths, mastodons, and passenger pigeons.

No one supports extinction of magnificent animals. Why should we permit extinction of our skies? Everyone has a right to the stars. Light pollution is the earliest and most visible sign of environmental destruction. The dome of light hanging over most cities blots out the stars, and electricity is wasted to light the night sky -- light needs to be on the ground not up in the sky. The wasted electricity represents needless burning of coal, oil, and natural gas, whose byproducts show up as acid rain, smoke, and carbon dioxide emission. Strip mining and underground mines produce the coal used for much of the wasteful burning, and runoff from this mining pollutes rivers and streams.

Thus, light pollution is far more than some astronomers being inconvenienced. It is a most harmful assault on the environment. It affects us all, and all of us ought to be concerned about it.


This is equivalent to saying why worry about the loss of trees and flowers in our cities. Why have urban parks? Just go out of town to see some grass, flowers, or trees. It shouldn't be necessary to go out of town to see them. If we can't have enough sense to plant trees, shrubs, and flowers all around our cities, we can at least have enough sense to plan for parks and preserve those green areas left. Why not have the same attitude toward dark skies? We are not asking people to turn off their lights. We are asking them to shield their lights, use proper lighting levels for the lighting task at hand, and turn off unneeded lights.

In any event, it is no simple task to get away from the lights. Urban sky glow, the dome of light hanging over all cities of any substantial size, extends for miles and miles. For example, it is easy to see the sky glow of Phoenix, Arizona, from more than 100 miles away. The sky glow from Los Angeles, California, is visible from an airplane 200 hundred miles away. How many dark spots are left in the urban corridor in the Northeastern part of the United States? Even in the most remote portions of North America, there are dusk to dawn lights blaring into the darkness. The light from one of these causes significant light trespass a mile or more away. We challenge anyone reading this essay to find a mountain top or plateau in the continental United States where there is no trace of light pollution visible somewhere on the horizon.



This is a frequent response when we ask people why they are not more active in the light pollution struggle, and it's tough to answer. Yes, the problem is enormous, growing in many areas, and very difficult to grasp fully. This doesn't mean it isn't worthy of effort. We have barely begun to fight. Just because we have a very big problem on our hands and presently few resources to bring to bear, doesn't mean we can't ultimately win. It's way too early in the struggle to say it's impossible to do anything about light pollution. Only recently has a small fraction of the public and astronomical community awakened to the problem. Only recently have we realized there are solutions to most lighting difficulties. There are now excellent fixtures available for all lighting needs. This is one of those few problems whose solution is eminently sensible, available, and saves money in both the short and long terms.

If you expect to rid a large city of its sky glow in the next year, then you will be very disappointed. If you want to get rid of local sources of light trespass, such as a dusk to dawn light next door or an unshielded street light on the corner, then you have a very good chance of accomplishing your goals with persistent but not obnoxious effort. You also have a reasonable chance for changing laws and instituting proper lighting techniques in your community. Over a long period of time, good lights will replace the bad ones. There will be a gradual slowing of the loss of dark skies and then an actual darkening of skies in some areas. This will not happen quickly, but it is possible. It will take incredible amounts of work and determination, but it can be done.


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