Dark Sky Lighting

Dark Sky Lighting

Valuing dark skies

By JD Brown

May 2015

For at least half a century, astronomers have paid witness to the debilitating effects of artificial light on the night skies. In more recent years, growing science and our own innate understanding of a disconnection has led us to better understand that we are all suffering from a lack of dark skies. We not only suffer a human and spiritual disconnect without dark skies but there are also costs for our health and the environment. Cities and towns across the country have attempted for several years to adopt local laws to limit the adverse impacts of artificial light on the night sky.

The International Dark Sky Association (IDA) has been at the forefront of this effort. IDA summarizes the primary damaging effects of artificial light as three-fold: (1) artificial skyglow – the diffused, pervasive light on the horizon; (2) glare – the visual discomfort and reduced visibility caused by lights that are too bright and not shielded from view; and (3) light trespass – unwanted light reaching across property lines and into natural habitats.

There are many different approaches to the control of the adverse impacts of artificial light. Some general categories of regulations that have been put in place by cities include:

  • Reduction in the overall amount of artificial light;

  • Redesign of light fixtures to improve shielding, angle lights downward, limit glare, change color spectrum and increase efficiency;

  • Elimination of light trespass;

  • The setting of curfews for unnecessary lighting; and

  • Amortization (phasing-in) of improvements.

Courtesy of IDA

Courtesy of IDA

In 2000, IDA provided language for the adoption of a Pattern Lighting Code in its Outdoor Lighting Code Handbook. This pattern code has been revised and updated by Christian B. Luginbuhl from the Flagstaff Station of the U.S. Naval Observatory. “Pattern” in this context refers to an effort to regulate the total amount of light per area consistently across the landscape regardless of the specific land uses present. The pattern code creates rough zones for differentiation (such as rural versus urban and residential versus non-residential), but for the most part sets forth a consistent, easy to apply pattern for light regulation.

Several cities have used this type of pattern approach in their own codes, including: Flagstaff, Arizona; Coconino County, Arizona; and Madison, Wisconsin.  Beginning in 2005, IDA teamed up with the Illuminating Engineering Society (IES), a lighting industry non-profit, to develop an alternative Model Lighting Ordinance (MLO). The primary distinction from the pattern approach is that the MLO takes into account the level of development on a site and permits more light as development on the site increases. The MLO also provides a mechanism for regulating individual light fixtures through a rating system it has named the “BUG” (Backlight-Uplight-Glare) system.

The MLO has been subject to some criticism on the basis that it permits developed areas, such as cities, to emit more light based on the concentration of development. Critics argue that the MLO creates the potential for these areas to emit more light than is currently emitted in unregulated areas.

“BUG” Rating System

“BUG” Rating System

The current recommendations of IDA probably lie somewhere in between these two model code concepts because in 2014 IDA worked with the City of Malibu, CA, to develop a lighting ordinance. IDA’s recommendation for Malibu, based on Malibu’s limited complexity and size, was to adopt a scaled back version of the MLO that incorporates many elements of the Pattern Lighting Code.

It can be difficult to determine which approach may be most effective. The answer may be that the right choice may vary by city. Any jurisdiction that wants to address the adverse impacts of artificial light should contact organizations like IDA and Flagstaff Dark Skies Coalition, as well as the many cities that have had codes in place for some time. It is also important for cities to recognize that the science and technology related to the control of light pollution is continuing to evolve and that, to be the most effective, cities will need to periodically reevaluate how well their efforts are working.

In a recent interview with Paul Bogard, author of The End of Night, I asked him about his preference for the regulation of artificial light. He expressed a preference for focusing on the design of light fixtures. His rationale being that establishing design criterion for light fixtures addresses a principal limitation for regulating artificial light, which is enforcement. Easily recognizable light fixtures help cities identify when sites are in conformance.

Bogard also expressed a preference for a system of regulation that allows individuals to take steps to limit their own impacts by purchasing available, certified dark sky fixtures at their local hardware store. Encouraging and even incentivizing land owners to invest in dark sky fixtures addresses one of the other primary hurdles for successfully controlling the adverse impacts of artificial light, which is the ability to phase-in new lighting and replace “grandfathered” fixtures.

After our interview with Paul, I wondered to myself to what degree am I able to experience the night sky. Surely in my hometown, I could get a piece of the night sky in my own backyard. That night I left the blinds open to bask in the darkness; unfortunately, at 3am I had to get up and close the blinds because it was too light too sleep.

Good Neighbor Lighting

Good Neighbor Lighting