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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]
minimum brightness [42] −1.47: star system Sirius: seen from Earth Brightest star except for the Sun at visible wavelengths [45] −0.83: star Eta Carinae: seen from Earth apparent brightness as a supernova impostor in April 1843 −0.72: star Canopus: seen from Earth 2nd brightest star in night sky [46] −0.55: planet Saturn: seen from Earth
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
Consequently, a magnitude 1 star is about 2.5 times brighter than a magnitude 2 star, about 2.5 2 times brighter than a magnitude 3 star, about 2.5 3 times brighter than a magnitude 4 star, and so on. This is the modern magnitude system, which measures the brightness, not the apparent size, of stars.
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.
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 Strömgren photometric system, abbreviated also as uvbyβ or simply uvby, and sometimes referred as Strömgren - Crawford photometric system, is a four-colour medium-passband photometric system plus Hβ (H-beta) filters for determining magnitudes and obtaining spectral classification of stars.
An object's surface brightness is its brightness per unit solid angle as seen in projection on the sky, and measurement of surface brightness is known as surface photometry. [9] A common application would be measurement of a galaxy's surface brightness profile, meaning its surface brightness as a function of distance from the galaxy's center.