Dark-sky movement

Dark-sky lighting

Dark-sky lighting is a concept important to the dark-sky movement, as it minimizes light pollution. The concept was started in the 1950s by the city of Flagstaff, Arizona. Flagstaff is a city of over 70,000 people, but because of its effectively controlled lighting, the skies are dark enough to see the Milky Way, and the light dome over the city viewed from some distance has been measured as less than 10% as bright as that over a similarly-sized city (Cheyenne, Wyoming) that has not sought to protect its night skies. Lights should be shielded on the top and sides so light doesn't go up to the sky and only used when needed (use motion detectors and only the wattage necessary). To minimize the visual brightness of skyglow and reduce glare and most other biological impacts, amber-colored lighting is critical (such as formerly high- and low-pressure sodium, or now amber LED. DarkSky International certifies fixtures as dark sky friendly, and these will have the DarkSky Approved seal.

Skyglow

Main article: Skyglow

Skyglow is the illumination of the night sky or parts of it, resembling an orange "smog". It occurs from both natural and human-made sources. Artificial skyglow is caused by the over-illumination of the sky from large city centres, shopping centres, or stadiums. It consists of light that is either emitted directly upward or reflected from the ground that is then scattered by dust and gas molecules in the atmosphere, producing a luminous background or light dome. These artificial skyglows cause the sky to be up to 100 times brighter in urban areas than a naturally dark sky that is unaffected by artificial light. Natural skyglow can come from natural light sources, such as the Sun, the Moon, the stars, or auroras.

Some communities are becoming aware of this problem and are putting forth efforts to minimize the hazy, orange skyglow. A community in particular is the city of Merritt, British Columbia. An article published July 8, 2010 states that they are making minor changes to lighting in and around Merritt, such as the installment of down-cast lighting to commercial buildings, as part of their light pollution abatement program. The benefits of this technological change include "saving energy through better focused lights, preserving the environment by reducing excess light that may affect flora and fauna, reducing crime and increasing safety by more adequately illuminating areas, and reducing health risks."

Scotobiology

Main article: Scotobiology

Scotobiology is the study of the role darkness plays in living organisms. It shows that the interruption of darkness by light pollution creates drastic effects for most organisms, changing their food gathering and feeding habits, their mating and reproduction behavior, or their migration behavior (in birds and insects) and social behavior. Approximately 30% of vertebrates and 60% of invertebrates are nocturnal, meaning that they depend on darkness. Their everyday behaviors are biologically evolved to adapt in uninterrupted darkness.

Dark-sky preserves

Main article: Dark-sky preserve

Dark-sky preserves are the main contributors to the dark-sky movement. They are protected areas commonly found in national parks or remote regions having a zero light pollution policy.

As of 2025, there are 200 worldwide locations covering over 160000 km2 of protected land and night skies in 22 countries on 6 continents.

The Dark Sky Places program has the intent to restore the nighttime environment and protect communities and wildlife with clear night skies having importance to nature, education, culture, and history. A list of designated dark sky places is maintained by DarkSky International

DarkSky International

Main article: DarkSky International

DarkSky International, formerly the International Dark-Sky Association (IDA), began in 1988. A non-profit, it manages the Fixture Seal of Approval program, which offers a third-party rating system judging the "sky-friendliness" of lighting fixtures. As of 2025, DarkSky International recognizes over 200 Dark Sky Places worldwide. DarkSky International advances dark sky awareness and protection through promotion of guidelines developed in collaboration with lighting industry partners (e.g. IESNA). The principles of responsible outdoor lighting are:

• Meets the needs of people to see at night
• Conserves energy
• Avoids harmful effects on wildlife
• Protects our night sky

List of groups

• Campaign for Dark Skies (UK)
• Canadian Geographic (Canada)
• CieloBuio (Italy)
• International Dark-Sky Association
• National Dark-Sky Week (United States)
• Niue
• Royal Astronomical Society of Canada (Canada)

References

References

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2. Chepesiuk, Ron. (January 2009). "Missing the Dark: Health Effects of Light Pollution". Environmental Health Perspectives.
3. "Lighting, Crime and Safety".
4. "Light Pollution Taking Toll on Wildlife, Eco-Groups Say".
5. "Light Pollution".
6. [http://azdailysun.com/news/state-and-regional/astronomers-celebrate-veto-of-billboard-bill/article_e5f59f64-3a22-5881-8015-4babce8253b2.html AZ Daily Sun: "Astronomers celebrate veto of billboard bill"]{{dead link. (January 2018)
7. "EnviroNews Archives - Scotobiology – The Biology of Darkness".
8. http://www.darksky.org/about-ida {{Webarchive. link. (2015-07-11 International Dark Sky Association: About the IDA)
9. Atkinson, Nancy. (2011-12-11). "A Refreshing Idea! Vote for Enabling City Kids to See Starry Skies".
10. "Flagstaff's Battle for Dark Skies – Flagstaff Dark Skies Coalition".
11. "Save our stars: City seeks to preserve night skies in Fort Collins". Coloradoan.
12. "Measuring the color and brightness of artificial sky glow from cities using an all-sky imaging system calibrated with astronomical methods in the Johnson-Cousins B and V photometric systems". American Astronomical Society.
13. "The Flagstaff Solution". Flagstaff Dark Skies Coalition.
14. "Outdoor Lighting Basics".
15. Reagan, Drew. (15 March 2025). "DarkSky Approved Luminaires".
16. http://www.lrc.rpi.edu/programs/nlpip/lightinganswers/lightpollution/skyGlow.asp Lighting Resource Centre: "What is sky glow?".
17. Loehr, Kaleena. (July 8, 2010). "Sky glow burning out?". Merritt News.
18. "Light Pollution – conference proceedings".
19. Scott R. Parker, S. L. (2011). Dark Skies, Bright Minds. Sources of Knowledge Forum, Ontario, Canada, pp. 12–17.
20. Regan, Margaret. (13 April 2017). "Arizona Sky Village's residents have one rule: 'Turn off your goddamned lights'". The Guardian.
21. Frumin, Aliyah. (21 August 2017). "Love to stargaze? Welcome to Sky Village, the darkest town in America". Today.com.
22. Polakis, Tom. (26 April 2004). "Arizona Sky Village".
23. (2025). "International Dark Sky Places". DarkSky International.
24. (1 June 2023). "We have a new name and logo".