The International Astronomical Union – Without dark skies, astronomers are unable to receive the faint signals of light from distant objects in outer space. Dark skies are a critical scientific resource for understanding the mysteries of the universe. Dark skies are also an important part of the cultural and natural heritage of all civilizations.
Many astronomical observatories are built in remote locations in an effort to escape the light of cities and towns. Even so, these observatories are threatened by light pollution such as city lights encroaching upon the mountaintop of Mauna Kea, Hawaii. Mauna Kea Observatories is one of the best astronomical sites in the world. Lighting ordinances are an important tool to protect these sites from light pollution.
How can we effectively reduce the impacts of light pollution? The most effective way is simply to turn off or reduce the amount of lighting. The change from white to yellow light also makes a major difference. We can plant more trees to reduce secondary reflections. Using fully shielded light fixtures to prevent light from shining upward is also helpful. Secondary reflections play a more important role in rural areas than in cities. Therefore, the solutions we describe above have a more significant impact in rural areas.
More details on light pollution can be found in a compilation of important findings by experts worldwide in the area of light pollution. The information was gathered under the umbrella of the Cosmic Light programme, organized by IAU during the International Year of Light 2015. You can download this brochure prepared by IAU Office for Astronomy Outreach here: