History of Science and Technology Colloquium

Despite the novelty of sunspot study in the Latin West, Galileo placed no particular emphasis on pitfalls in either the observational process or the visual presentation of his data: in the second of his Letters on the Sunspots, the camera obscura and the ephemeral phenomena it was designed to show figure as curiously available to all. While Galileo emphasized the naturalness and inevitability of the engravings that accompanied his work—or, better, the irrelevance of their prehistory as traced projections of the sunspots—his rival Christoph Scheiner masked his own reliance on the camera obscura with frequent and misleading references to his direct observations of the sun and to the inaccuracy of his hand-drawn sketches. In this lecture I will examine the strategies adopted by both observers in the earliest phase of the debate, and I will use the sunspot images produced through direct observation by the English scientist Thomas Harriot in this same period to evaluate the logic of their arguments, and the strengths and limits of these visual data.