magnitude relation

Norman Robert Pogson

Asteroids discovered: 8
42 Isis May 23 1856
43 Ariadne April 15 1857
46 Hestia August 16 1857
67 Asia April 17 1861
80 Sappho May 2 1864
87 Sylvia May 16 1866
107 Camilla November 17 1868
245 Vera February 6 1885
Norman Robert Pogson (born March 23, 1829 in Nottingham – died June 23, 1891) was an English astronomer.

By the time he was 18 years old, he had computed the orbits of two comets. He became an assistant at Radcliffe Observatory in Oxford, England in 1851. In 1860 he travelled to Madras, India, becoming the government astronomer. At the Madras Observatory he produced the Madras Catalogue of 11,015 stars. He also discovered five asteroids and six variable stars.

His most notable contribution was to note that in the stellar magnitude system introduced by the Greek astronomer Hipparchus, stars of the first magnitude were about a hundred times as bright as stars of the sixth magnitude. His suggestion in 1856 was to make this a standard, so each decrease in magnitude represented a decrease in brightness equal to the fifth-root of 100 (or about 2.512). The Pogson Ratio became the standard method of assigning magnitudes.

The magnitude relation is given as follows:

m_{2} - m_{1} = -2.5 log_{10} (L_2 / L_1)

where m is the stellar magnitude and L is the luminosity, for stars 1 and 2.

In 1868 and 1871, Pogson joined the Indian solar eclipse expeditions.

During his career he discovered a total of eight asteroids and 21 variable stars. He headed the Madras Observatory for 30 years until his death.


The following celestial features are named after him:


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