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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 .
The darkness of the night sky is classified on the Bortle scale from 1 ("excellent", i.e., extremely dark) to 9 ("inner-city sky", i.e., partially dark). Hanle is categorised as an excellent dark astronomical site with Bortle colour key "Black". [9] The dark sky is important for the conservation of nocturnal animals and ecology.
Beta Phoenicis (β Phoenicis, β Phe) is a binary star in the constellation Phoenix. Its apparent magnitude is 3.30, [2] meaning that it can be seen with the naked eye (see Bortle scale). The distance to Beta Phoenicis is poorly known.
The most prominent meteor showers, occurring on approximately the same dates every year, are the Perseids, named for the constellation Perseus and peaking on the night of August 12-13; the ...
Eta Cephei (η Cep, η Cephei) is a star in the northern circumpolar constellation of Cepheus. With an apparent visual magnitude of 3.4, [2] this is a third magnitude star that, according to the Bortle Dark-Sky Scale, is readily visible to the naked eye. Parallax measurements put it at a distance of 14.37 parsecs (46.9 light-years) from Earth. [1]
Time was reckoned by the position marked off in constellations on the ecliptic in which the Moon rises daily in the course of one lunation (the period from New Moon to New Moon) and the Sun rises monthly in the course of one year. These constellations (nakṣatra) each measure an arc of 13° 20 ′ of the ecliptic circle. The positions of the ...
In Hindu astronomy, there was an older tradition of 28 Nakshatras which were used as celestial markers in the heavens. When these were mapped into equal divisions of the ecliptic, a division of 27 portions was adopted since that resulted in a clearer definition of each portion (i.e. segment) subtending 13° 20′ (as opposed to 12° 51 + 3 ⁄ 7 ′ in the case of 28 segments).
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.