Editing Light pollution (section)

===Light trespass===

Light trespass occurs when unwanted light enters one's property, for instance, by shining over a neighbour's fence. A common light trespass problem occurs when a strong light enters the window of one's home from the outside, causing problems such as [[sleep deprivation]]. A number of cities in the U.S. have developed standards for outdoor lighting to protect the rights of their citizens against light trespass. To assist them, the [[International Dark-Sky Association]] has developed a set of model lighting ordinances.<ref name="International Dark-Sky Association">[https://web.archive.org/web/20081122040258/http://www.darksky.org/programs/model-lighting-ordinance.php International Dark-Sky Association]. darksky.org</ref>

The [[International Dark-Sky Association|Dark-Sky Association]] was started to reduce the light going up into the sky which reduces the visibility of stars (see Skyglow below). This is any light that is emitted more than 90° above [[nadir]]. By limiting light at this 90° mark they have also reduced the light output in the 80–90° range which creates most of the light trespass issues.
[[File:Phoenix Lights from afar.jpg|thumb|The city of Phoenix, seen from {{convert|55|mi}} away in [[Surprise, Arizona]]]]

U.S. federal agencies may also enforce standards and process complaints within their areas of jurisdiction. For instance, in the case of light trespass by white [[strobe]] lighting from communication towers in excess of [[Federal Aviation Administration|FAA]] minimum lighting requirements<ref>{{cite web| title = AC 70/7460-1K Obstruction Marking and Lighting| date = 2007-02-01| url = http://wireless.fcc.gov/antenna/documentation/faadocs/7460-1K.pdf| access-date = 2009-07-04| archive-url = https://web.archive.org/web/20100527213109/http://wireless.fcc.gov/antenna/documentation/faadocs/7460-1K.pdf| archive-date = 2010-05-27}}</ref> the [[Federal Communications Commission]] maintains an Antenna Structure Registration database<ref name="FCC Antenna Structure Registration">{{cite web|title = FCC Antenna Structure Registration|url = http://wireless.fcc.gov/antenna/index.htm?&job=home|access-date = 2009-07-04|archive-url = https://web.archive.org/web/20090207035625/http://wireless.fcc.gov/antenna/index.htm?&job=home|archive-date = 2009-02-07}}</ref> information which citizens may use to identify offending structures and provides a mechanism for processing citizen inquiries and complaints.<ref name="fcc.gov">{{cite web|title = FCC Consumer & Governmental Affairs Bureau|url = http://www.fcc.gov/cgb/cgb_offices.html#CICD|publisher = U.S. Federal Communications Commission|date = March 2011|access-date = 2006-12-03|archive-date = 2010-08-10|archive-url = https://web.archive.org/web/20100810191544/http://www.fcc.gov/cgb/cgb_offices.html#CICD|url-status = live}}</ref> The [[U.S. Green Building Council]] (USGBC) has also incorporated a credit for reducing the amount of light trespass and sky glow into their environmentally friendly building standard known as [[Leadership in Energy and Environmental Design|LEED]].

Light trespass can be reduced by selecting light fixtures that limit the amount of light emitted more than 80° above the nadir. The [[Illuminating Engineering Society of North America|IESNA]] definitions include full cutoff (0%), cutoff (10%), and semi-cutoff (20%). (These definitions also include limits on light emitted above 90° to reduce sky glow.)