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Brightness magnitudes


An ancient Greek astronomer named Hipparchus (190 B.C.E.- 120 B.C.E.) invented the first Magnitude scale to measure the brightness of stars. He gave the brightest stars he could see a value of 1 and the dimmest a value of 6.

For example, Sirius was the brightest star in sky with a value of -1.6.

Star brightness magnitude.


In ancient times, stars were ranked in six magnitude classes, but presently it is used the system proposed by Norman Robert Pogson in 1850. One magnitude is defined as a ratio of brightness of 2.512 times (5√100).

For example, a star of magnitude 5.0 is 2.512 times as bright as one of magnitude 6.0.