Credit: Lisa Crawford Bruhn
David L. Crawford, an astronomer and one of the pioneers of the modern dark sky movement, died peacefully on July 22 in Carlsbad, California.
During his decades of work at Kitt Peak National Observatory (KPNO) in Tucson, Arizona, he was recognized for his work in stellar photometry and directed the construction of two of the most productive 4-meter telescopes in the world.
But his most impactful legacy may not lie in any single instrument, but in his leadership role in the fight to preserve dark skies for all. He was one of the founders of the International Dark-Sky Association (IDA), today known as DarkSky Internationaland worked to educate local officials and the public about the fragility of the night sky and the best lighting practices to preserve it. Her tireless efforts and skillful coalition-building helped Southern Arizona municipalities adopt some of the most stringent lighting codes in the world.
Today, the movement he helped start has gone globalIDA has certified hundreds of dark sky sites in 22 countries around the world, and its work has helped raise awareness of the importance of the night sky as a resource and part of humanity's shared cultural heritage.
“I personally consider Dave one of the greatest environmentalists of the late 20th and early 21st centuries,” wrote IDA co-founder Tim Hunter. in a sentence published by the organization. “Dave brought the issues of light pollution, light intrusion and quality night lighting to the forefront of public consciousness.”
Crawford also served as chairman of the American Astronomical Society's committee on light pollution. “In many ways, Dr. Crawford was the founder of the modern dark sky movement, and we owe much to his vision and leadership,” the committee said in a statement. statement(The group is now known as the Committee for the Protection of Astronomy and the Space Environment, or COMPASSE.)
From astronomer to lawyer
Crawford was born in 1931 in Tarentum, Pennsylvania, and received his Ph.D. from the University of Chicago, where he worked as a research assistant at the institution's affiliated Yerkes Observatory in Williams Bay, Wisconsin. After a brief stint at Vanderbilt University in Nashville, Tennessee, he joined the Kitt Peak team in 1960, where he would spend the remainder of his research career. From 1963 to 1973, he served as project manager for the construction of the Nicholas U. Mayall Telescope at KPNO and its southern counterpart, the Victor M. Blanco Telescope atop Cerro Tololo in Chile. The Mayall and Blanco telescopes remain major facilities for the study of dark energy, each conducting cutting-edge studies of distant galaxies with the Dark Energy Spectroscopic Instrument and the Dark Energy Camera, respectively.
At Kitt Peak, Crawford established himself as a leader in the fight against light pollution by founding KPNO's Dark Sky Office with colleague Bill Robinson. Along with other observatories, they convinced local officials in Arizona and Mexico to move toward low-pressure sodium lighting, which emits at wavelengths that could be easily filtered out with professional installations. “We don't want Southern Arizona to go the way of Southern California, where we're losing the maximum utility of several important observatories because of unrestricted growth in outdoor nighttime lighting,” Crawford told KPNO. Astronomy in the July 1982 issue.
Their work took on another dimension a few years later, when he was contacted by amateur astronomer Tim Hunter. As Hunter recounted, the skies above his personal observatory in Tucson had recently been filled with wayward light from the nearby University Medical Center. It turned out that the center had installed the low-pressure sodium lighting recommended by professional astronomers like Crawford, but without shielding, significantly reducing sky quality for amateur astronomers. After several meetings with Crawford and Robinson, Hunter said, “What initially began as a contentious discussion gradually developed into a friendship and a shared commitment to protecting the night sky.”
Crawford and Hunter founded IDA in 1988. In August of that year, Astronomy He noted that the new organization was not adopting “an 'anti-light' tactic in the battle against light pollution,” but rather aimed to “promote the use of 'good light,'” including properly shielded luminaires.
“For many years, IDA headquarters was his home, with boxes of papers, notebooks, computers, lamps, slides, brochures and books scattered around his living room, his home office and his work office at (KPNO) headquarters in Tucson,” Hunter said.
Crawford was also a member of the Illuminating Engineering Society, the organization for lighting professionals. “He wanted to learn about lighting and work with professionals who designed and installed lighting,” Hunter said. “His goal was to make friends, not enemies.”
In August 1988, Crawford organized a colloquium in Washington, DC, sponsored by the International Astronomical Union. In November of that year, Astronomy reported:
According to Crawford, this was the first meeting to bring together astronomers from around the world with lighting engineers, lawyers and government officials concerned about the dangers facing astronomy. Unless these problems are resolved, Crawford said in his opening address at the colloquium, “observational astronomy will end.”
Thirty-six years later, the meeting's themes seem eerily prescient. In addition to terrestrial light pollution, astronomers expressed concern about interference from satellites (both in radio astronomy and in the form of streaks in images), as well as the growing threat of space debris to orbiting telescopes.
Crawford served as IDA's executive director for approximately 20 years. During those years, the pages of Astronomy Reports of his work appeared frequently, as did notices of meetings and colloquia at which he spoke on the topic, converting untold numbers of audience members to his cause. (His recruits included Sky and telescope Senior editor Kelly Beatty, who served on the IDA board for many years and wrote a… Tribute to Crawford can be found here.)
An inspiration that transcends generations
When Astronomy In an article about the founding of the IDA published in our August 1988 issue, Hunter said: “If only manufacturers could be persuaded to make only suitable and protected lights, much of the problem would be solved within a generation.” Just eight years later, in September 1995, Astronomy Progress was reported on this front:
Thanks to the educational efforts of Crawford and the IDA, lighting manufacturers are producing better fixtures and, perhaps more importantly, are making these fixtures available to cities, towns and counties across the country. Recently, Hubbell Lighting, Inc., came out with a kit to retrofit the classic 175-watt “cobra” head fixture. It is estimated that there are more than 10 million of these lights hanging from poles, homes, barns and sheds across the country. For a one-time cost of about $45, the light can be retrofitted with a guard that converts the dreaded fixture into a full-cut fixture and a 70-watt lamp. Because the light is directed downward, the same amount of light still reaches the ground, while the fixture owner realizes savings for several years without loss of effectiveness.
Over the past decade, the impact of such luminaires on the night sky has gained importance. turn for the worseespecially as municipalities and businesses have acted quickly to install LEDs. The technology allows for greater energy savings, but the overuse of unprotected broadband LEDs has introduced a new round of threats to astronomy, cultural heritage, wildlife and human health, such as Christopher Cokinos in detail in our July 2024 issue.
Related: How to win the battle against light pollution
Moreover, the space dangers to astronomy identified 36 years ago by Crawford and his colleagues have only been amplified by megaconstellations like SpaceX's Starlink.
These multiplying threats make the work Crawford started even more crucial, and it will be up to our generation to finish it. As the fight against light pollution continues, Crawford’s legacy of forging coalitions between astronomers, environmentalists, engineers and policymakers will remain a model to follow for many years to come.
