He discovered eight asteroids, the first, (42) Isis, in 1856. It was in connection with the light curves of variable stars, his other main interest, that he introduced a mathematically rigorous definition of stellar magnitudes based on a logarithmic scale (see pogson ratio; pogson scale). Others, notably the German scientist Carl August von Steinheil (1801–80), had proposed similar scales, but Pogson’s advocacy led to its adoption as a universal standard.