Flagstaff's Dark Sky Heritage

Flagstaff, Arizona has a 60-year tradition of dark sky preservation, beginning with a 1958 ordinance to ban advertising searchlights. The current ordinance, enacted in 1989, is the most comprehensive in the world; it specifies not only shielding and maximum illumination requirements, but strict control of the emission spectrum via use of low pressure sodium (LPS) lamps. As of the end of May 2019, LPS lamps have been discontinued by lighting manufacturers, so Flagstaff, like many cities worldwide, will be switching its outdoor street lighting system to LEDs. We have spent several years working with City staff to develop what will again be world-leading standards in outdoor illumination, making extensive use of narrow band amber (NBA) and phosphor-converted amber (PCA) LEDs rather than white LEDs. We have already installed NBA and PCA test fixtures in several areas around town, and retrofit of all 3,700 fixtures in Flagstaff should occur in the next 2-5 years. These standards will set the precedent for other applications such as commercial properties and parking lots (pictured below). In this iPoster, I will review the history of dark sky preservation in Flagstaff, the current state of affairs in outdoor lighting, the types of LEDs available, their impact on the night sky, and how Flagstaff will preserve its exceptionally dark sky in the LED era.