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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 .
Note that the brighter the star, the smaller the magnitude: Bright "first magnitude" stars are "1st-class" stars, while stars barely visible to the naked eye are "sixth magnitude" or "6th-class". The system was a simple delineation of stellar brightness into six distinct groups but made no allowance for the variations in brightness within a group.
Stars in binary systems (or other multiples) are listed by their total or combined brightness if they appear as a single star to the naked eye, or listed separately if they do not. As with all magnitude systems in astronomy, the scale is logarithmic and inverted i.e. lower/more negative numbers are brighter.
about 400,000 times as bright as mean full Moon −25.60: star Sun: seen from Mars at aphelion: −25.00: Minimum brightness that causes the typical eye slight pain to look at: −23.00: star Sun: seen from Jupiter at aphelion −21.70: star Sun: seen from Saturn at aphelion −21.00: star Sun: seen from Earth on an overcast midday measuring ...
c. 300 BC — star catalog of Timocharis of Alexandria; c. 134 BC — Hipparchus makes a detailed star map; c. 150 — Ptolemy completes his Almagest, which contains a catalog of stars, observations of planetary motions, and treatises on geometry and cosmology; c. 705 — Dunhuang Star Chart, a manuscript star chart from the Mogao Caves at Dunhuang
Sky Quality Meter model SQM-L. A sky quality meter (SQM) is an instrument used to measure the luminance of the night sky, more specifically the Night Sky Brightness (NSB) at the zenith, with a bandwidth ranging from 390 nm to 600 nm. [1]
In doing so, he also developed the brightness scale still in use today. [1] Hipparchus compiled a catalogue with at least 850 stars and their positions. [ 2 ] Hipparchus's successor, Ptolemy , included a catalogue of 1,022 stars in his work the Almagest , giving their location, coordinates, and brightness.
The UBV Photoelectric Photometry Catalogue, or UBV M, is the star brightness catalogue that complies to the UBV photometric system developed by astronomer Harold Johnson. Evolution of the UBV Photoelectric Photometry Catalogue