Moon crater, circa 1850s. Salted paper print from a Collodion negative. Although this photograph seems to show a moon crater, it is actually a photograph of a papier-m璽ch矇 or clay model owned by astronomer John Herschel. At the time, it was technically impossible to take close-up views of the lunar surface. This crater, full of distinctive features, is labeled "Copernicus" at right. A scale showing the size of the crater in miles can be seen at upper left. John Herschel (1792-1871) was the son of astronomer Sir William Herschel, and he extended many of his father's astronomical observations. He established the Slough reflecting telescope near Capetown, South Africa, won the Copley Medal of the Royal Society for his Cape Observations (1847), and made important contributions to other branches of science. As a photographer, he invented the process of fixing film using hyposulphite of soda and coined the terms positive and negative.