content: Both; photographic plates were being used at this time, eyepieces however still played a major role. This particular observatory (Detroit lol / University of Michigan) I can't properly describe the photographic imaging history and methodology, however I do know that there was an extension to the building in 1909 which included the construction of a photographic room, 3 years before the OP picture. Spectrographs were used in the observatory's research, I'm not sure when they were first used.  Eyepieces were definitely used before and after 1912. Research done includes the discovery of 22 asteroids, Comet Schaeberle II and Schaeberle IV, studies and construction of various lunar tables. The baboons running around in Detroit today wanted this historical 1852 building and frontier of astronomical research demolished, however it will be preserved.