Night Skies at Homestead National Monument
The National Park Service and the Night Skies
The National Park Service (NPS) is committed to "…conserve the scenery and the natural and historic objects and the wildlife therein and to provide for the enjoyment of the same in such manner and by such means as will leave them unimpaired for the enjoyment of future generations" (NPS Organic Act of 1916). This commitment includes the night skies and the lightscape of the parks. The NPS Night Skies division is committed to helping parks monitor the effects of light pollution and offer suggestions for the mitigation of any issues that may be present. Dan Driscoe, an NPS employee with the Natural Sounds and Night Skies Division said in 2001 "Unlike losing a species to extinction, topsoil to erosion, or virgin lands to development, the night sky is 100% recoverable."
The National Park Service defines a natural lightscape as the resources and values that exist in the absence of human-caused light at night time. Natural lightscapes are critical for night time scenery and nocturnal habitat. There are many species that depend on natural patterns of light and dark for navigation, predation and other natural processes. Light pollution can have a negative effect on the organisms within a park and can also reduce the enjoyment of park visitors.
What is Light Pollution?
Light pollution is the introduction of artificial light either directly or indirectly into the natural environment. Light pollution degrades the view of the night sky by reducing the contrast between faint extraterrestrial objects and the background of the luminous atmosphere. An example of light pollution is sky glow, sometimes referred to as artificial sky glow, light domes or fugitive light; which is the brightening of the night sky from human caused light scattered into the atmosphere. Another form of light pollution is glare, which is the direct shining of light. Both of these forms of light pollution impact the human perception of nighttime, natural landscapes and features of the night sky.
Night Sky Study at Homestead National Monument of America
In 2008 the NPS Night Skies division collected baseline data at Homestead National Monument of America in an effort to create baseline data regarding light pollution. A special camera was used to capture images that show different levels of light pollution at night. These images can help measure the amount of brightness and glare that occurs in the area captured by the images. With these images it is also possible to identify the sources of light pollution and help separate the amount of natural verses manmade brightness.
For more information on the methods used by the Night Sky staff please visit: http://www.nature.nps.gov/night/methods.cfm
Cleaning up Light Pollution
Light pollution is fortunately something that is very correctable. Studies have shown that light fixtures that direct all light downward greatly reduce the amount of light pollution. These are referred to as shielded lights. Some of the light will still reflect off the ground and scatter throughout the sky, but it is less than with older style lighting fixtures. Light pollution can also be reduced by utilizing a less powerful bulb. Some of the newer bulbs coming out in the market can greatly decrease the degradation of the night sky by light pollution. Small changes in lighting fixtures and light bulbs can make huge improvements resulting in better visibility, improved safety and less energy use. For more information go to: http://www.darksky.org/outdoor-lighting
Park sites all look at the same questions regarding the use of outside lighting:
· Why is this area being lit?
· When should it be lit?
· How many lumens are adequate?
· What spectrum of light is most beneficial?
· What are the safety and security issues in this location?
· How can we improve the quality of the visitor experience while saving energy, minimizing glare, decreasing light pollution, and reducing the impact on wildlife?
FOR ADDITIONAL INFORMATION VISIT: