image description: a photo of the night sky, edited to show increasing levels of light pollution, from left to right. Each level is labeled as follows (with a description of what the sky looks like at each level added by me): *1 Excellent Dark Sky Site - No light pollution present. the Milky Way is visible, and the sky is full of stars. *2 Dark Sky Site - Very little light pollution present. Only slightly dimmer than the previous level. *3 Rural Sky - Little Light Pollution. Dimmer than previous level, but Milky way is still visible. Noticably fewer stars than level 1, though. *4 Suburban/Rural Transition - Increasing light pollution the more suburban it is. Milky Way just barely visible, fewer stars visible. *5 Suburban Sky - Light pollution beginning to really dominate the night sky. Only the brightest parts of Milky Way visible, signifigantly fewer stars visible. *6 Bright Suburban Sky - A lot of Light Pollution Present. Few Stars are visible, the Milky Way is no longer visible except for a handful of very bright points *7 City/Suburban Transition - Signifigant levels of Light Pollution beginning to be present, especially the closer to the city center you get. The Milky Way is no longer visible at all, and only the brightest of stars are visible (a very small number in all, with whole sections of the night sky completely devoid of visible stars). *8/9 City/Inner City Sky - The two highest levels of light pollution. The sky never gets very dark at all, with not even the brightest stars visible. Image Source: European Southern Observatory (ESO)/P. Horálek, M. Wallner, via wikipedia Additional Image Information: (copied from wikipedia) "This image illustrates the Bortle scale, which measures the impact of light pollution on the dark skies at a given location. It shows, from left to right, the decrease in the number of stars and night-sky objects visible in excellent dark sky conditions compared with cities. The illustration is a modification of an original photograph taken at ESO's Paranal Observatory in Chile, a place with excellent dark-sky conditions, perfect for astronomy. The image has been flipped left to right."
The Bortle scale was developed by amateur astronomer John E. Bortle in the February 2001 edition of Sky & Telescope magazine to help skywatchers evaluate and compare the darkness of an observing site. It has since seen wider use in other fields of science like biology to study the impact of light pollution on the environment.
further reading:
Researchers show how light pollution can harm imperiled bats
DarkSky International restores the nighttime environment and protects communities from the harmful effects of light pollution through outrea
Light pollution, or artificial light at night (ALAN), is a rapidly growing threat to nocturnal wildlife around the world, particularly for b
Bats are nocturnal animals that have adapted to a life in darkness, partly to avoid predation during daylight hours from bird of prey specie
