LIGHTING AND ASTRONOMY

摘要

All light is not created equal; all uplight is not equally polluting. Not only professional observatories, but many national parks, wilderness areas, and rural communities away from cities around the world are affected at significant distances by skyglow arising from light used in cities. When considering the effects of artificial light escaping from an urban environment, the direction into which the light is propagating is critical. This paper discusses both the relative impacts of light emitted into various directions above horizontal, as well as the relative impacts of small amounts of uplight emitted into "typical" directions arising from unshielded fixtures. The results show that uplight emitted near the horizontal has 20 to 100 times the sky glow impact of light emitted toward the zenith, even when near-ground blocking is taken into consideration. Further, even very small amounts of direct uplight from partially shielded fixtures, since it is typically heavily directed near horizontal, has a similarly large effect, typically much larger than potential decreased amounts of total lighting that might be possible when such partially shielded fixtures are used.