In the summer of 1645, the Oratorian Virgilio Spada (1596–1662) acquired a painting of a debate on astronomy by the Sienese artist Niccolò Tornioli (1598?–1651) and displayed it in the Palazzo Spada, the Roman residence of his older brother, Cardinal Bernardino Spada (1594–1661). Our discussion of The Astronomers questions some of the traditional identifications of its characters, although we cannot claim to have solved these figures’ identities and several remain a mystery. We do present new iconographic interpretations of particular scientific instruments, diagrams, and natural phenomena in the canvas. These novel readings occasionally remain conjectural in part because Tornioli represents these entities in a way that makes it clear that he did not fully comprehend them. The errors and obscurities in Tornioli’s painting lead us to two conclusions. First, that the erudite Virgilio Spada was unlikely to have been involved in the definition of the painting’s iconographies, as he would have objected to Tornioli’s crass mistakes and obscure imagery. Second, that these errors and indistinct details should be taken at face value, insofar as they accentuate the difficulties of astronomical observation. Beyond highlighting these challenges, we argue that the painting also visualizes techniques for countering them. Specifically, the canvas would have focused early modern observers’ attention on the edifying powers of civil conversations and communal observations with scientific instruments as well as images—including diagrams, celestial maps, and paintings.

Tim’s Vermeer is a recent documentary feature film following engineer and self-described non-artist Tim Jenison’s extensive efforts to “paint a Vermeer” by means of a novel optical telescope and mirror-comparator procedure. His efforts were inspired by the controversial claim that some Western painters as early as 1420 secretly built optical devices and traced passages in projected images during the execution of some of their works, thereby achieving a novel and compelling “optical look.” We examine the proposed telescope optics in historical perspective, the difficulty and efficacy of the mirror comparator procedure as revealed by an independent artist/copyist’s attempts to replicate the procedure, and the particular visual evidence adduced in support of the comparator hypothesis. Specifically, we find that the luminance gradient along the rear wall in the duplicate painting is far from being rare or difficult to achieve, as was claimed; in fact, such gradients appear in numerous Old Master paintings that show no ancillary evidence of having been executed with optics. There is indeed a slight bowing of a single contour in the Vermeer original, which one would nominally expect to be straight; however, the optical explanation for this bowing implies numerous other lines would be similarly bowed, but in fact all are straight. The proposed method does not explain some of the most compelling “optical” evidence in Vermeer’s works, such as the small disk-shaped highlights, which appear like the blur spots that arise in an out-of-focus projected image. Likewise, the comparator-based explanations for the presence of pinprick holes at central vanishing points, and the presence of underdrawings and pentimenti in several of Vermeer’s works, have more plausible non-optical explanations. Finally, an independent experimental attempt to replicate the procedure fails overall to provide support for the telescope claim. In light of these considerations and evidence we conclude that it is extremely unlikely that Vermeer used the proposed mirror-comparator procedure.

Waywiser, is the online database of the Collection of Historical Scientific Instruments, Harvard University. It was first developed by Jean-François Gauvin and Sara J. Schechner in 2007--2008, and has since been updated in format by Juan Andres Leon and other museum staff. As curator of the Collection, Schechner is the contributor of thousands of object entries and biographies, particularly in the areas of astronomy, microscopy, optics, time finding, horology, surveying, navigation, psychology, and radio. Work on the database is ongoing. The database is named after an ancient instrument for measuring distance, also called a hodometer.