By David Levy
When you go outside on the summer nights, and the sky is clear, how many stars do you think you see? If you are in the middle of a large city like Tucson, you might see fewer than a hundred stars. However, from the darker sky over Vail, it is possible to see several thousand stars; typically, on a good night, you can see over 3000 individual stars. Don’t bother counting all of these; instead, I would recommend that you simply look up and enjoy the multitude of stars up there.
My first experience with light pollution took place while I was a child growing up in the Montréal suburb of Westmount, Québec. During the 1960s, as the city of Montréal prepared for its great World’s Fair of 1967, I could easily see the light dome increase in brightness over the city, especially to the east. It was actually an amazing thing to watch; year after year the eastern sky grew brighter and brighter, even as my observing activities grew stronger. The only real break to which I could look forward were the three summer experiences I was able to enjoy at the Adirondack Science Camp south of Plattsburgh, New York, in the United States. The sky there was dark and pristine, and it remains so to this day. Going to that camp was like partaking in a miracle.
As I grew older, I longed to experience a dark sky year-round. That dream came true when I relocated to Arizona, where the sky was (and is) especially valuable and dark, first from my home in Corona de Tucson, and later from the home and Observatory that my wife, Wendee, and I share here in Vail. Not only is the sky dark, but it is also clear most of the time; unlike the sky over the northeastern part of North America, the Arizona sky is often spectacularly clear, dark.
I knew the sky was dark, but I never really understood how dark, and more importantly, how to keep it dark, until I met Tim Hunter and the international dark sky Association. Tim began the organization as the result of a little argument he had with Dr. David Crawford, a well-known astronomer at Kitt Peak National Observatory. Knowing that Crawford had put a lot of effort into changing the light fixtures surrounding the Tucson headquarters of the observatory, Tim pointed out that while the new fixtures would not interfere with the mighty spectroscopes and telescopes used by the professional astronomers, these fixtures would interfere with the work done by amateur astronomers throughout the state of Arizona. This
little argument began a decades-long friendship that led to the establishment of the International dark Sky Association. Over the next few decades the organization has leapfrogged forward. It now has over 10,000 members and is run by a board of directors and a small staff in an office in North Tucson. The mission of the IDA is “to preserve and protect the night time environment and our heritage of dark skies through quality outdoor lighting.”
This is the purpose, and the magic, of the International Dark Sky Association. It is also part of the magic that IDA does not want no night lights, just safe and unobtrusive night lights. We will never be able to enjoy the Milky Way or distant galaxies from the centers of large metropolitan areas, but by moving out just a little bit we can enjoy many of the same glorious sites that our great-grandparents were able to see many generations ago. There are still spots in the United States that allow for near-perfect observing. Vail, or at least portions of it, is one such spot. For more information I invite you to visit www.darksky.org.
What are the most important concepts dealing with light pollution? The first is glare. Glare happens when a light on the night shines so brightly that it can bother your ability to see clearly. Glare can affect night driving; after driving along a dark stretch of road, you suddenly encounter a brightly lit gas station. As your eyes struggle to adapt to the sudden increase in light, you may miss seeing an oncoming car. A second issue is light trespass. The easiest way to illustrate this is to imagine your neighbor’s light shining into your bedroom window, keeping you awake at night. When I was growing up in Montréal, the streetlight in front of our home shone into my sister’s room; at the time we were able to get the city of Westmount to paint the back part of that light with black paint, which reduced significantly the amount of light entering our home. A third issue is the shielding of lights. Ideally, full cutoff lights that do not cast their glows upward into the sky are ideal, but we can live with other types of fixtures that are somewhat successful at reducing glare without cutting it off completely; these are called partial cut-off fixtures. Lights that do not cast glare into the night sky, and lights that are shielded, are the best weapon to protect our vision at night, and our night sky.
Finally, at last year’s Tucson Festival of books, I had the honor of introducing Paul Bogard, who had just completed his book The End of Night: searching for natural darkness in an age of artificial light. It is an excellent book. I thoroughly enjoyed
