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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.
See the Bortle scale.) There is even variation within metropolitan areas. For those who live in the immediate suburbs of New York City, the limiting magnitude might be 4.0. This corresponds to roughly 250 visible stars, or one-tenth of the number that is visible under perfectly dark skies.
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Area codes are also assigned for non-geographic purposes. The rules for numbering NPAs do not permit the digits 0 and 1 in the leading position. [1] Area codes with two identical trailing digits are easily recognizable codes (ERC). NPAs with 9 in the second position are reserved for future format expansion.
NPA Year Current region 212: 1947 New York City: Manhattan only; overlays with 332, 646, and 917 : 315: 1947 Syracuse, Utica, Watertown, and north central New York; overlaid by 680.
A new area code is coming to the Upstate. By next summer, 821 will be added as a prefix to the current 864 area code. The South Carolina Public Service Commission on Nov. 28 announced the new area ...
This is a list of telephone area codes of Pennsylvania. In 1947, the American Telephone and Telegraph Company divided Pennsylvania into four numbering plan areas (NPAs) and assigned distinct area codes for each. Since 1995, several relief actions in form of area code splits and overlays have expanded the list of area