The paper describes the author's witnessing of images projected from an eighteenth-century solar microscope made by John Dollond, now at the Deutsches Museum in Munich. Peter Heering facilitated this session as part of his research on the solar microscope. A rectangular mirror, the length of a hand, mounted outside a museum window caught the sunlight and directed it indoors into the microscope's optical tube with its specimen. Astonishing detail was displayed in the resulting image projected onto a screen at human height. Crisply delineated scales patterned the image cast by a historical specimen of a butterfly wing. Observers interacted fluidly with these images in the very dark room. In sharing what we noticed, questioned and conjectured, we contributed to a temporary community. These participant interactions relate to Steven Shapin and Simon Schaffer's notion that, in the seventeenth century, Robert Boyle used witnessing as a ‘collective act’. Here, the ‘collective act’ spanned participation across history. For example, Robert Hooke's 1665 Micrographia inspired Philip and Phylis Morrison's workshop during my college years and their collaboration with the Eames Office on a film depicting travel through ‘powers of ten’, based on Kees Boeke's 1957 picture book. Personal memories were extended and informed by historical experiences, both for Robert Hooke's subsequent interpreters and for Peter Heering's participants.