Creating the ImagesPhotographing the night sky was itself quite labor-intensive. Because the earth rotates, the observer had to carefully guide the telescope throughout the night in order to create an unblurred image of the object under observation. This was difficult to accomplish, especially given the length of exposure time required to capture the light of distant bodies. In his copybook, Charles Perrine wrote an early reflection on the merits of astrophotography, one page of which has been scanned and displayed here. He discusses the difficulty of capturing the light of nebulae, noting that the action of guiding the telescope often resulted in the loss of structural detail. The copybook itself is on display in Case 1: In Relation to Nature. Barnard also discusses the labor of the process in his 1913 book Photographs of the Milky Way and of Comets.
Most of the images produced at the Lick were recorded as negatives on glass plates coated with photosensitive chemicals. After working through the night, astronomers often continued to work into the morning, developing the negatives they had created. They often found that the images were overexposed, underexposed, or blurry. We have in this archive only a few of the thousands of images created by Lick astronomers, as many were rejected. Many of the original glass negatives created with the telescopes are still housed on the grounds of the Lick Observatory.
Reproducing the ImagesThese images and documents tell us how difficult it was for astronomers to create these early images of the cosmos, speaking to a certain intensity of labor on the part of the individual astronomer. At the same time, they also archive another story about how these aesthetic concerns impacted the labor of the printers in meeting the expectations of the Lick's directors.
The Lick sent successful images to photogravure (engraving) companies around the country, seeking out the most skilled photographic technicians to create faithful duplicates of the images they had worked so carefully to create. Yet even the best images were often difficult for the printers to reproduce. As you can see with the plates displayed here, the actual object under observation often measured only millimeters in diameter on the plate. The printer was to transfer the image on the glass plate onto a copper plate or another kind of glass plate, which was then coated in ink to produce a print. The creation of the second plate positive was a long process which involved re-exposing the negative onto photosensitive materials--materials that were thicker, more viscous, and more unstable than the chemicals used to create paper prints now; and then dipping the plate in a bath of acid in order to etch into it the light portions of the image, leaving a raised image on the plate to be coated in ink. Accordingly, the very materiality of these materials and the difficulty of manipulating them often interfered with the printers' attempts to carry the exact resolution and sharpness of the original image over to the second plates. Edward's Barnards book, mentioned above, also covers the printing process in detail. To read more about the reproduction process, see Alexander Pang's article on astrophotography at the Lick, cited at the bottom of this page.
Astronomers could not know what many of these distant, often invisible objects actually looked like; they were working within certain ideas about what they should look like and how to best represent them to the public. They wanted to create visually stunning photographs. Their letters to the photogravure companies had many complaints--loss of light or structural detail, the lack of clarity and contrast, the "thinness" or lack of depth or "darkness" of the sky behind the object. Their complaints were often aesthetic in nature; and as researcher Alexander Pang has noted, they often invented new aesthetic discourse or concepts--like "nebulosity" and "snappiness"--to describe to the printers how a cosmic body should appear. The Lick's directors often required the printers to try again, in order to darken the background, or to bring out important details from the original image--like the fainter light in a nebulae or very thin lines within comet's tails. Yet they would then express concern to the printers that the prints were too retouched and therefore not truly objective pieces of data.
To see more glass plates and images of celestial bodies, and a greater selection of letters exchanged between Lick directors and printing companies, see our digital exhibit.
As noted above, our research in this area builds on the work of Alexander Pang.