American photographer who was devoted to the studies of astronomy by his passion for the comets, becoming professional astronomer. He showed great talent for observation and was considered the Dean of American seekers of comets: thirty years had already found more than 10, using their knowledge of photographic technique.
After becoming an astronomer from the Lick Observatory of Mount Hamilton, St. Clear (California), discovered, in 1892, Amalthea, the fifth satellite of Jupiter. In 1889 began to photograph in detail the milky way, demonstrating that the dark regions are not real empty, but which are determined by the presence of gases and dust that absorb light from the more distant star. Result of this work was his photographic Atlas of selected areas of the milky way, posthumous publication in 1927. In 1892-93 discovered, with the 36-inch (91 cm) of the Lick Observatory refractor, the craters of Mars, noting details of the planet never before warned by the astronomers Giovanni Schiaparelli and Percival Lowell. However, these observations were not published when he was still alive.In 1916 she discovered the largest known proper motion star, a red star located at a distance of six light-years, which is fast approaching the Sun, precisely called Star Barnard. See Ophiuchus.