1829, died at Starfield, Crowborough, Sussex, 17 July 1904, who spent his whole life in the search after Truth, and the endeavour to add to the happiness of others. This stone is erected in loving devotion by his widow Dorethea Roberts née Klumpke." Through a donation of his wife Dorothea in honor of her late husband, the Société astronomique de France (the French Astronomical Society) established the Prix Dorothea Klumpke-Isaac Roberts for the encouragement of the study of the wide and diffuse nebulae of William Herschel, the obscure objects of Barnard, or the cosmic clouds of R.P. Hagen. This biennial prize was first given in 1931 and continues today. The crater Roberts on the far side of the Moon was named to jointly honour Isaac Roberts and the South African astronomer Alexander William Roberts. Interest in astronomy In 1878, Roberts had a 7-inch refractor at his home in Rock Ferry, Birkenhead. Although at the time he used this for visual observation, he began to explore stellar photography, his forte, a few years later. In 1883, Roberts began experimenting with astrophotography. He first used portrait lenses with apertures varying from ⅜ to 8 inches (9.5mm to 203mm). Roberts was pleased with the results, and ordered a reflecting telescope with a silver-on-glass mirror of 20-inch diameter (100-inch focal length) from the Grubb Telescope Company and by 1885 he had built an observatory building to house it. He mounted photographic plates directly at the prime focus to avoid the loss of light that would occur from using a second mirror. This allowed him to make significant progress in the then-developing field of astrophotography. In 1886 Roberts displayed his first photographs at the Royal Astronomical Society at Liverpool, of which he was president. These images showed, for the first time, "the vast extensions of nebulosity in the Pleiades and Orion." Advancements Astrophotography requires very long exposure times (sometimes an hour or more) to record faint objects on a photographic plate. Long exposure could also record objects invisible to the human eye. Isaac Roberts developed a technique of "piggyback" astronomical photography, mounting the camera/lens on a larger equatorial mounted telescope that was used as a "guidescope". The combination kept the camera aimed accurately over the long exposure time as the Earth rotated. Most consider Roberts' magnum opus to be a photograph showing the structure of M31, the Great Nebula in Andromeda (now known as the