Also found in: Encyclopedia, Wikipedia.
(Astronomy) the brightness ratio of two celestial objects that differ by one magnitude. On the Pogson scale a difference of 5 magnitudes is defined as a difference of 100 in the intensities of two stars; therefore a difference of 1 magnitude is equal to the fifth root of 100, i.e. 2.512
[C19: named after N. R. Pogson (1829–91), British astronomer]