Wheeler and Marvel reply: The International Dark-Sky Association does valuable work to preserve precious dark skies. Through education, outreach, and consultation with lighting designers and policymakers, the association promotes more efficient use of nighttime lighting to reduce light pollution. We endorse the association’s activities. The American Astronomical Society has been an affiliated organization of the IDA for years, one of us is a lifetime member, and many AAS members and astronomy institutions are active in the association as well. However, we believe that the IDA will draw members principally through its accomplishments and the value they provide.
The membership of the IDA is growing rapidly. The association currently has nearly twice as many members as the AAS. Even if all US AAS members joined, IDA membership would only increase by about 20%. Roberts correctly states that the IDA is composed of “astronomers and others.” What he does not make clear is that the others far outnumber the astronomers who are members, and rightly so. Light pollution predominantly affects the general public. Poor nighttime lights threaten our health and safety, put migrating wildlife at risk, waste energy and money, and deprive countless millions of the beauty of the nighttime sky.
Light pollution, radio-frequency interference, and space debris are all issues of concern to the AAS. All of these detrimental aspects of human technology can potentially limit our ability to make astronomical observations. Light pollution certainly does negatively affect ground-based astronomy. Astronomers have either removed their telescopes to sites where the impact is minimal or worked with local communities—for example, in Tucson, Arizona, and in the West Texas counties surrounding McDonald Observatory—to reduce the growth of light pollution. Both efforts have been successful.
Light pollution will be controlled through the public’s recognition of its detrimental effects on life in general, not through its impact on the small number of research observatories or the relatively small number of professional astronomers in the world. We applaud the IDA and its continued efforts, and we pledge to continue our support for its work.
