Title graphic for the exhibit: From Eyeballs to Electrons page title: Starlight in Silver

Sagittarius star cloud Star clouds in Sagittarius.

By the time of Lick Observatory's founding, a few astronomers had begun to experiment with photography to record their observations, but visual observing was still the rule. Indeed, Lick's Great 36-inch Refractor, completed in 1888 and then the world's most powerful telescope, was originally designed for visual work.

Photography dates from about 1825, but the insensitive emulsions and cumbersone processes of early photography made it impractical for astronomy. Fifty years of refinement were required before it took root at the telescope, but in the end its takeover was rapid and complete. By the early twentieth century, the photographic plate had put an end to most visual observing by professional astronomers, and would dominate the field for decades. The human eye—the astronomer's only detector for all of history—had been replaced by silver crystals suspended in gelatin on a sheet of glass (learn more about the photographic process).

Photographic plates offered two overwhelming advantages. First, they could accumulate light over long exposures, at last freeing astronomers of the limit imposed by the eye's rapid refresh rate. Beautfully detailed images of objects far too faint for the eye to detect could build up in the photo-sensitive emulsion. By making much fainter objects "visible," photography effectively expanded the observable universe manyfold. Second, photographic observations left permanent records, free of observer bias, for later study.

Click on the thumbnails below for more on early astrophotography at Lick Observatory. plate of the moon, 1893 Moon, 1893 photographic plate holders in carrying box Plate holders early photographic plates Early plates photographic plates in a drying rack Pleiades, 1898 Gaertner measuring machine Measuring machine