After working as an assistant at the South Villa Observatory in 1851, he moved to the
Radcliffe Observatory in
Oxford in 1852. Despite Pogson's isolation he had at the time of his death discovered 134 stars, 106 variable stars, 21 possible variable stars and 7 possible supernovae. Pogson also made special expeditions, observing a total solar eclipse on 18 August 1868 at
Masulipatnam and making spectrometric studies. His most important contribution was to note that in the
stellar magnitude system introduced by the
Greek astronomer
Hipparchus, stars of the first magnitude were a hundred times as bright as stars of the sixth magnitude. Pogson's suggestion in 1856 was to make this a standard; thus, a first magnitude star is 1001/5 or about 2.512 times as bright as a second magnitude star. This
fifth root of 100 is known as '''Pogson's Ratio'''. The magnitude relation is given as follows: :
m1 - m2 = -2.5 log10 (
L1 / L2) 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. He received a telegram from
Ernst Friedrich Wilhelm Klinkerfues on 30 November 1872 which read
Biela touched Earth on 27th. search near Theta Centauri, a message so esoteric that it caught the fancy of the newspapers of the time. Unfortunately the skies were cloudy in Madras and when it cleared up on 2 December 1872, he observed an object (recorded as
X/1872 X1) which he believed to be a return of
Biela's Comet but was later found to be a different object which has been called "Pogson's comet". One of Pogson's assistants was
Chintamani Raghunatha Chary. He worked for many years with Pogson and his retirement in 1878 was a blow to Pogson. Pogson also got into increasing difficulties with his collaborators in England as well as the bureaucracy in India. George Airy, who had admired Pogson once became increasingly unsupportive and downright dismissive of Pogson's applications for help from the government as well as to help him return to England. Pogson on his part had been stubborn in not supporting a southern-sky survey. Pogson served for 30 years at Madras, taking no leave during the period. His health declined and he died in June 1891. He is buried at
St. George's Cathedral, Chennai. ==Family life==