The dark-sky movement is a campaign by people who want to reduce light pollution. Advantages include making more stars visible at night, reducing the effects of unnatural lighting on the environment, and cutting down on energy usage. Earth Hour and National Dark-Sky Week are two examples of such efforts.
The movement started with professional and amateur astronomers alarmed that nocturnal skyglow from urban areas was blotting out the sight of stars. For example, the world-famous Palomar Observatory is threatened by sky-glow from Escondido and local businesses. For similar reasons, astronomers in Arizona helped push the governor there to veto a bill in 2012 which would have lifted a ban on illuminated billboards.
The movement has spread with groups like the International Dark-Sky Association, as other concerns have been raised. For example, according to the Burlington Free Press nocturnal animals can be harmed by light pollution because they are biologically evolved to be dependent on an environment with a certain amount of hours of uninterrupted daytime and nighttime. The over-illumination of the night sky is affecting these organisms (especially birds). This biological study of darkness is called scotobiology. Light pollution not only affects animals and plants, but also energy costs in the U.S alone are 2.2 billion due to over-lighting. Light pollution has also been found to affect human circadian rhythms.
The dark-sky movement works to encourage the use of full-cutoff fixtures that cast little or no light upward in public areas and generally to encourage communities to adopt lighting regulations. A 2011 project is to establish "dark sky oases" in suburban areas.
Sky glow 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 sky glow 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 sky glows cause the sky to be 5–10 times brighter in urban areas than a natural dark sky that is unaffected by artificial light. Natural sky glow can come from natural lighting sources such as the moon, the stars, the sun or auroras.
Sky glow affects the ability to view stars which can be troublesome for astronomers who rely on the night sky for their research. Astronomers usually prefer very dry, very dark nights for observation.
Some communities are becoming aware of this problem and are putting forth efforts to minimize the hazy orange sky glow. 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 effect flora and fauna, reducing crime and increasing safety by more adequately illuminating areas, and reducing health risks."
'The Ecology of the Night' conference created the concept of scotobiology. Scoto(darkness)biology(life) is the study the role of darkness plays in living organisms and how it limits how much light an organism can tolerate.
Humans have always given more credit to light as a biological benefit to an organism than the effects of darkness. Scotobiological studies have proved though that interrupted darkness by light pollution of the night skies holds drastic effects for most organisms; changing their food gathering and feeding habits, their mating and reproduction behavior, migration behaviour (birds and insects) and their social behavior. 30% of vertebrates and 60% of invertebrates are nocturnal, meaning that they depend on darkness. Their everyday behaviors are biologically evolved to adapt in unintereupted darkness. Light pollution would have the highest negative impact on these organisms.
Human health is also adversely affected by the effects of light pollution. Light during night time hours have been linked to human cancers and psychological disorders.
Dark-sky preserves are the main contributors to the dark-sky movement. They are a protected area found mostly in national parks that have a zero light pollution policy set in by the government and controlled by the National Dark Sky Association.
As of February 6, 2012, there was a total of 35 formally recognized dark-sky preserves recorded in the world with Canada in the lead containing 15 different preserves. These preserves are located in Nova Scotia, New Brunswick, Quebec, Ontario, Saskatchewan, Alberta and British Columbia. Other countries that have dark-sky preserves are the Czech Republic, Hungary, Poland, Slovakia, Spain, United Kingdom, and the United States.
The parks are put in place by the Dark Sky Places program with the intention to remind us that the night sky serves just as much importance to our culture and history as our day-time sky.
Canadian Geographic featured an article on dark-sky preserves in Canada. The top national park in Canada that has incorporated a dark-sky preserve is Jasper National Park, located in Jasper, Alberta.
International Dark Sky Association
The IDA (International Dark Sky Association) began in 1988 and is the only non-profit organization that puts efforts into preserving the night sky. They are the recognized authority for light pollution and are responsible for the "Fixture Seal of Approval program" which offers a third party rating system judging the "sky-friendlyness" of lighting fixtures and in 2009, opened a Public Policy and Government Affairs office in Washington, D.C to inform law makers and lobbyists on energy efficiency of outdoor lighting and to promote the adoption of energy saving measures. The IDA has implemented several simple guidelines to responsible outdoor lighting along with some practical considerations.
- In regards to safety, one needs only the right amount of light, in the right place, at the right time. More light often means wasted light and energy.
- Use the lowest wattage of lamp that is feasible. The maximum wattage for most commercial applications should be 250 watts of high intensity discharge lighting, but less is usually sufficient.
- Whenever possible, turn off the lights or use motion sensor controlled lighting.
- Incorporate curfews (i.e. turn lights off automatically after a certain hour when businesses close or traffic is minimal).
Following the guidelines put in place by the IDA insures that light pollution be kept at a minimum.
Some lighting distributors with fixtures approved by the IDA are:
- Green Earth Lighting (formerly Outdoor Lighting Associates)
- Home Depot
- Landscape Lighting World 
- Lighting Styles (UK Distributor) 
List of groups
- Campaign for Dark Skies (UK)
- CieloBuio (Italy)
- International Dark-Sky Association
- National Dark-Sky Week (US)
- Canadian Geographic (Canada)
- Royal Astronomical Society of Canada (Canada)
- Canadian Scotobiology Group (Canada)
- Merritt News
- Caltech Astronomy Department
- AZ Daily Sun: "Astronomers celebrate veto of billboard bill"
- http://isebindia.com/05_08/05-01-3.html International society of environmental botanists: "Scotobiology – The biology of darkness"
- http://www.darksky.org/about-ida International Dark Sky Association: About the IDA
- Universe Today IDA Suburban Outreach Sites
- http://www.lrc.rpi.edu/programs/nlpip/lightinganswers/lightpollution/skyGlow.asp Lighting Resource Centre: "What is sky glow?".
- http://www.lrc.rpi.edu/programs/nlpip/lightinganswers/lightpollution/skyGlow.asp Lighting Resource Centre: "What is sky glow?"
- http://www.merrittnews.net/article/20100708/MERRITT0101/100709954/-1/MERRITT/sky-glow-burning-out Merritt News: "Sky glow burning out?" author: Kaleena Loehr
- Scott R. Parker, S. L. (2011). Dark Skies, Bright Minds. Sources of Knowledge Forum, (pp. 12–17). Ontario.
- http://www.darksky.org/index.php?option=com_content&view=article&id=564 International Dark Sky Association: "International Dark Sky Places
- http://www.darksky.org/about-ida International Dark Sky association: "About the IDA"
- http://www.darksky.org/index.php?option=com_content&view=article&id=745 International Dark Sky Association: "Simple guidlines for lighting regulations.