He made several large reflecting telescopes, including the 36-inch (0.91-m) Crossley Reflector later acquired by Lick Observatory. From 1880 he used another 36-inch instrument for photography, obtaining the first good pictures of the comet now designated C/1881 K1, and the first photograph of the Orion Nebula to record its filamentary structure. This, and other time exposures of subjects such as Jupiter and Saturn, were made possible by the accurate drive mechanism that he installed on the telescope.