This paper explores the various meanings of precision during the early modern period in Europe. In contrast with existing literature focused on assessing the precision of early instruments, this study delves into the intended significance of the term ‘precision’ as understood by historical figures such as J. Stöffler, P. Nunes or F. Mordente. By analysing a selection of instruments equipped with scales, both in their physical form and as they are described in instrument texts, several facets of precision emerge. Some (...) findings demonstrate that the precision of scales can be enhanced through corrections obtained from tables. In other cases, visual estimation is substituted with a method for obtaining values of multiple sexagesimal places. Furthermore, certain instruments designed to represent theoretical concepts achieve greater precision by incorporating the most intricate details of these notions. This investigation into lesser-known meanings of precision underscores the need of comprehensively exploring the concepts, the practices and the terminology surrounding precision that were in use over the fifteenth and sixteenth centuries. (shrink)

In what way does the construction of three-dimensional spherical models in the early modern period reflect the search for an appropriate representation of subtle, slow changes perceived in the firmament of the fixed stars? The present paper analyses some of the preserved models and assesses the potential they held to stimulate contemporary thinking on this question, termed the “motion of the eighth sphere.” The spheres discussed here reveal different ways of conceiving and visualizing stellar precession, which was more commonly expressed (...) in tabular form, such as the Alfonsine tables, or by means of theoretical texts, such as Peurbach’s Theoricae novae planetarum. One of the spheres unexpectedly turns out to be the only known material representation of Johannes Werner’s alternative theory of trepidation. Although our knowledge of the context in which these spheres were produced is limited, their material characteristics point to their distinct origins. A focus on the rare and understudied species of “trepidation spheres” leads to questions not addressed in studies drawing only on written sources. It brings additional actors into the spotlight, in particular instrument-makers. Moreover, the variety of constructions found in the group of surviving spheres indicates that the available traditional sources allowed for variant interpretations. Besides texts and diagrams, the trepidation spheres are historical tools of thought that can literally be touched. While further investigation is needed, this paper looks at the spheres’ potential role for practitioners in exploring the geometric implications of trepidation in Alfonsine astronomy from the second half of the 15th century onwards. (shrink)

Mathematical instruments in the early-modern period lay at the intersection of various knowledge traditions, both practical and scholarly. Scholars treated instrument-related questions in their works, while instrument makers and mathematical practitioners also put much energy into producing instrument books. Assessing the role of that literature in the exchange of knowledge between the different traditions is a complex task. Did it directly influence workshop practice? Here, I will examine instruments from a famous Louvain workshop ca. 1570, focussing on the role of (...) printed images. I will suggest that woodcuts did indeed inspire instrument makers; that images were sometimes more important than the text; and that the viewer’s appreciation of the images depended upon his familiarity with an instrument’s mathematical structure. -/- . (shrink)

In this article, we publish the critical edition of Andalò di Negro’s De compositione astrolabii, with English translation and commentary. The mathematician and astronomer Andalò di Negro presumably redacted this treatise on the astrolabe in the 1330s, while residing at the court of King Robert of Naples. The present edition has three purposes: first, to make available a text missing from the previous compilations of works by Andalò di Negro; second, to revise a privately circulated edition of the text; and (...) third, to help disseminating one of the rare Latin texts presenting the principles of the stereographic projection which underlie the construction of the astrolabe. (shrink)