Our project (446722167) combines photographic history and history of science to interrogate the role and importance of photographic materials and practices in shaping and re-configuring astronomy in the era of glass plate photography. Aside from paper catalogues of stars, the routine work with and on glass plates left a trail of marks, notes, and labels made or fixed directly on the plates. These traces, together with industrial information about plate manufacture and supply, photographic emulsions and pre-exposure treatments are important indicators of the performance of astronomical knowledge-making through glass plate photography. Our research moves beyond contemporary scholarship’s reliance on photography in print by revealing how it was used by scientists in their painstaking, day-to-day practices and techniques, and how standards were established for manufacture and use of glass plate photography in astronomy and further afield. In both cases the materiality of photography will be central. We aim to show that the “information” contained on these glass objects extends beyond the image. They index large transnational markets in photographic raw and finished materials; issues of storage, preservation, maintenance; and global networks of observatories consolidating scientific practices. Based on extensive archival research at collections in Germany, UK, USA, and the Netherlands, we detail the emergence of epistemic cultures at the observatory that remediated and implicated new spaces, labor, technologies, and personnel. In addition to the ecological and ontological implications of these cultures for the history of photography and science, the migration of photographs through global systems involved the imperial, colonial, and postcolonial dimensions that will be taken seriously in this calculus of transnational networks.