Norman Pogson. Portrait of the British astronomer Norman Robert Pogson (1829-91). He was an assistant at the Radcliffe Observatory in Oxford, England, and by 1860 was government astronomer at Madras, India. There he devised Pogson's ratio to define stellar magnitudes. For example first magnitude stars are slightly more than 2.5 times brighter than second magnitude stars and so on. This magnitude scale is still used today.