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The Bortle dark-sky scale (usually referred to as simply 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 is an American amateur astronomer. He is best known for creating the Bortle scale to quantify the darkness of the night sky. Bortle has made a special study of comets. He has recorded thousands of observations relating to more than 300 comets. From 1977 until 1994 he authored the monthly '"Comet Digest" in Sky and Telescope magazine.
The Bortle scale is a nine-level measuring system used to track how much light pollution there is in the sky. A Bortle scale of four or less is required to see the Milky Way whilst one is "pristine", the darkest possible.
The nine chapters of Bogard's book map to the nine levels of the Bortle scale, which attempts to quantify the subjective brightness and suitability for astronomy of the sky in different environments. Bogard has said of the scale, invented in 2001, "one of the reasons why identifying different depths of darkness is so important is that we don't ...
The scale used to indicate magnitude originates in the Hellenistic practice of dividing stars visible to the naked eye into six magnitudes. The brightest stars in the night sky were said to be of first magnitude ( m = 1), whereas the faintest were of sixth magnitude ( m = 6), which is the limit of human visual perception (without the aid of a ...
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Created the Bortle scale to quantify the darkness of the night sky. Robert Burnham Jr. (1931–1993), author of the Celestial Handbook . Andrew Ainslie Common (1841–1903), built his own very large reflecting telescopes and demonstrated that photography could record astronomical features invisible to the human eye.
According to the Bortle scale, it can be viewed from dark suburban skies. Based upon an annual parallax shift of 15.12 mas as seen from Earth, [1] this star is located around 223 light years from the Sun. It is advancing in the general direction of the Sun with a radial velocity of −11.6 km/s. [4]