Hier is net so `n lusmaker:
The Bortle Dark-Sky Scale is a nine-level numeric scale that measures the night sky's and stars' brightness (naked-eye and stellar limiting magnitude) of a particular location. It quantifies the astronomical observability of celestial objects and the interference caused by light pollution and skyglow. John E. Bortle created the scale and published it in the February 2001 edition of Sky & Telescope magazine to help amateur astronomers compare the darkness of observing sites. The scale ranges from Class 1, the darkest skies available on Earth, through Class 9, inner-city skies.[1]
