Light Pollution

Lightning Images

Ludick Observatory


Click on image below to go to IDA website:


E-mail us

Phone us

Light Pollution: The Problem, The  Solutions
Abstract:  The problem of light  pollution exists most everywhere, and it is still growing rapidly.  Fortunately, there are solutions. The problem is a lack of awareness, including within the  astronomical community. There is a great deal of apathy and inertia to be overcome as well. However, progress is being made in a number of places. The  astronomical community must become much more involved if we are to preserve the quality of our nighttime skies, both for research and for the public. The beauty of the night sky is a wonderful thing to all. In addition, everything done to decrease the adverse urban sky glow also helps greatly to improve the quality of  night lighting. With good lighting, we improve visibility, safety, and security,  as well as minimizing energy waste, and we have a much more comfortable nighttime environment. There are resources to help, within the astronomical  community and the lighting industry, and these are growing. The International Dark-Sky Association has a great deal of information that is most helpful; see  the Web site at

I. Introduction

For most people on earth, including we professional astronomers, the dark  skies our ancestors had have disappeared. The problem is urban sky glow, due mostly to too much bad lighting. It has adversely affected most all of our observing sites. And it is still getting worse in most locations.

There are solutions to the problem, but a key point is that we must join together in our efforts in attacking all this bad lighting, encouraging the use of only good nighttime lighting for all applications. With good lighting, we all win. We help preserve the dark skies, we see better at night (and are safer and  more secure), we have a more pleasant and comfortable nighttime environment, and  we save a great deal of energy and money doing so. Neither astronomers nor the public, anywhere, need any of the adverse environmental effects of poor  lighting. We should not tolerate it. We must do all we can, individually and organizationally, to preserve the beauty of the night sky, for astronomy and for all of mankind!

II. The Problem

There are many good reasons for artificial lighting at night: to help us see better, for security, safety, utility, and for an attractive nighttime environment around us. There is no way that nighttime lighting is going to disappear, even if there is another energy crisis. There are too many good reasons for such lighting. But not all lighting is good lighting. Far too much  of our present nighttime lighting does not meet its objectives. It is bad lighting. Let me list here the common components of bad lighting:

  1. Urban sky glow (the brightening skies over our heads), destroying our view of the universe. We don't live up there in the sky; we don't need all that light up there. It is a problem both for astronomers and for the general public, most of whom really enjoy the beauty of the night skies. It has been growing most  everywhere, and it has severely impacted operations at many existing  observatories. In those locations where it has not yet, you can be sure that it  will in time, if we are not able to implement solutions. This sky glow has also  removed the view of the universe from most of the public, the majority of which  are urban dwellers. It would be a crime if our children and their children lose  all of their view of the beauty of the night sky.
  2. Glare. Glare never helps visibility, but it is far too common in all of our  cities and in most lighting everywhere. We should strive for and accept only a glare free environment. Let's not be blinded by glare. Far too much present day lighting has glare; it is always bad.
  3. Light trespass. Many present lighting installations bother us as much or more than they help. The wasted light shines into our yards, our windows, even  our telescope buildings. As with noise pollution, we don't need any of these  intrusions. Such lighting is not meeting well the goals for which is was installed.
  4. A trashy looking, confusing nighttime environment. We should, all of us, be  striving for an attractive nighttime environment, just as we should be doing in  the daytime. Such poor environments are part of the stress of today's life. We  should help with the problem, not compound it. Remember, the night is part of  the environment, too.
  5. Energy waste. We waste an astronomical amount of energy and money by all this bad lighting, shining it where it is not needed or wanted (including up  into the sky) and by using energy inefficient light sources and lighting designs. Better to use such money for improving our world, not trashing it. In  the United States alone, over One Billion Dollars is wasted every year just to  light up the night sky.

III. There Are Solutions

We all suffer from these problems. But we need not, for fortunately there are  solutions. The key is quality nighttime lighting. Let me list briefly the  components of these solutions.

  1. Use only good lighting. Such quality designs are really all just common  sense approaches to lighting. Let's not tolerate all the bad lighting; let's get rid of it.
  2. Shine the light down, where it is needed. Control the light output to  locations where it is needed; don't waste it. Use quality lighting fixtures.
  3. Use time controls (or dimmers or other controls) to insure that light is there when needed, and not there when it is not.
  4. Design and install lighting to insure that glare is minimized. Most all  glare comes from poor fixtures or poor installations. There is no need for any of it.
  5. Use the right amount of light for the task, not overkill. "More light" is  not good design. When not blinded by glare, the eye is a marvelous instrument  and can see very well at what seems to be quite low lighting levels. In  addition, going from over-lit areas to darker areas means that we don't see too  well (transient adaptation), and the opposite holds as well.
  6. Use energy efficient light sources. Light sources vary greatly in their  efficiency. Consider especially the use of low pressure sodium lamps; they are  the most efficient of all, and they are also strongly preferred by astronomers since the light output by LPS is essentially all one color and can be filtered  out quite well. LPS is excellent for street lighting, parking lots, security  lighting, and other applications where color rendering is not critical. Careful  lighting design can be done using LPS for essentially any application.

IV. Progress in Implementing Solutions

Quality lighting design is being used now in many locations, such as Tucson. Such cities are benefiting by better lighting for their citizens, by a great  deal of energy savings, and by darker skies (but not darker streets). We all  really do win. Awareness of the problems and of the solutions is increasing rapidly, in the public area and especially in the lighting community.

The International Lighting Commission (CIE) and many national organizations  now have technical committees addressing the issues, and reports and  recommendations are pending. After all, who can be against good lighting rather  than bad, given all its advantages? I am an active member of most of these  committees, and I am pleased with the growing awareness and activities.

One effective method for communities to attack the problem is to appoint an  Outdoor Lighting Working Group to consider the issues and to recommend specific solutions tailored to local needs (including lighting control ordinances to set community standards; hundreds of these have now been enacted). Such "committees"  have been very effective in all locales where they have been implemented. They  have the added advantage of educating many people about the issues.

VI. So What's the Problem?

The main problem is that there is still a vast lack of awareness of the  issues, the problems, and the common sense solutions. Education is the main  thrust of most current activities. The second large problem is apathy. Even with awareness, action is needed. Some consider it too big an issue to become involved with, others feel that it is not important enough. Neither is a good  enough reason for apathy. Most astronomers are doing little or nothing to  educate themselves about the issues, much less to spend time working for  solutions.

VII. Help Is Available

The International Dark-Sky Association, a non-profit organization, is a  powerful ally to help anyone with their educational efforts. It is a membership-based organization with over 2000 members now from 70 countries. IDA has produced over 130 information sheets discussing the issues, and they are an  important resource for those who want to become informed and who want to help  spread the word to others. Check out IDA's Web site on the Internet ( which contains a lot of excellent information about the  issues and links to many other interesting sites. While there is a growing  awareness of the problems, and of the solutions, much more educational outreach is needed. IDA needs many more individual and organizational members and much more support from the astronomical community, nationally and internationally.

VIII. Conclusion

There is a problem with light pollution, for astronomy and for the public, and it is still getting worse most everywhere. However, there are solutions, and  they work. They also improve the quality and effectiveness of our nighttime lighting, and they help us save a great deal of energy and money. We know that  for sure. Lack of awareness and apathy are the main problems. Action is called  for. Now. By all of us. The bottom line is that "We All Win."

Please do help build awareness and overcome apathy, everywhere. The stars and  the universe need the support of us all. Join with us to help preserve mankind's view of the beauty of the night sky!
 David L. Crawford
The above content is an extract from the IDA Information sheet# 134. All writing courtesy of the IDA.

For more on the IDA and ideas and solutions, visit the IDA website.

Copyright © Astronomy FOR Africa.  2003 - 2010 All rights reserved