Bortle scale

In this 10-second exposure photo, facing south toward Sagittarius, light pollution obscures the stars and faintly visible Milky Way in the suburban night sky over Southern California.

The Bortle scale is a nine-level numeric scale that measures the night sky's brightness of a particular location. It quantifies the astronomical observability of celestial objects and the interference caused by light pollution. John E. Bortle created the scale and published it in the February 2001 edition of Sky & Telescope magazine to help amateur astronomers evaluate the darkness of an observing site, and secondarily, to compare the darkness of observing sites. The scale ranges from Class 1, the darkest skies available on Earth, through Class 9, inner-city skies. It gives several criteria for each level beyond naked-eye limiting magnitude (NELM). The accuracy and utility of the scale have been questioned in recent research.

单词	Bortle
释义	Bortle 原声例句 PBS太空科学 But most Americans live at Bortle scale 5 or higher, which means they aren't seeing 98% of the stars in the sky. 但大多数美国人生活在 Bortle 等级 5 或更高，这意味着他们看不到天空中 98% 的星星。英语百科 Bortle scale The Bortle scale is a nine-level numeric scale that measures the night sky's brightness of a particular location. It quantifies the astronomical observability of celestial objects and the interference caused by light pollution. John E. Bortle created the scale and published it in the February 2001 edition of Sky & Telescope magazine to help amateur astronomers evaluate the darkness of an observing site, and secondarily, to compare the darkness of observing sites. The scale ranges from Class 1, the darkest skies available on Earth, through Class 9, inner-city skies. It gives several criteria for each level beyond naked-eye limiting magnitude (NELM). The accuracy and utility of the scale have been questioned in recent research.
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