Astronomer, born 1792; 1871. Continued the stellar researches of his father and completed his work on luminaries and nebulae, made valuable photometric observations of stars magnitude, e.g., discovered that a star of the first magnitude Isaiah 100 times as bright as a sixth magnitude star, invented a reflector for telescopic observations, was the author of theory of meteoric origin of sun spots, initiated the use of the terms positive and negative in photographic representations, did research on the stellar distribution in heavens and drew up his famous catalog of southern stars.