Photographs of Stars, Star-Clusters and Nebulae

A geologist and fellow of the Royal Astronomical Society, Isaac Roberts (1829–1904) made significant contributions to the photography of star-clusters and nebulae. By championing reflecting rather than refracting telescopes, Roberts was able to perceive previously unnoticed star-clusters, and was the first person to identify the spiral shape of the Great Andromeda Nebula. Roberts' use of a telescope for photographing stars, and a long exposure time, provided greater definition of stellar phenomena than previously used hand-drawings. Although Roberts' conclusions about the nature of the nebulae he photographed were not always correct, the book is significant for the possibilities it suggests for nebular photography. Published in 1893 and 1899, the two-volume Photographs of Stars represents the summation of his work with his assistant W. S. Franks at his observatory in Crowborough, Sussex. Volume 2 contains 29 plates of stars, and his conclusions about their origins and nature.