This paper explores discussions centred on the activities of the British Board of Longitude to consider the ways in which some men of science, instrument makers and others thought about questions of precision and accuracy, both in principle and in terms of what was possible in practice when making observations at sea. It considers firstly the terminology used in some eighteenth- and early nineteenth-century texts, highlighting the concept of exactness, which was more commonly used to describe one of the desirable (...) qualities of instruments and methods. It then looks at some of the discussions and debates in which the Board of Longitude was involved from the 1760s to think about different actors’ expectations of what levels of exactness might be either desirable or possible for day-to-day navigation. The focus is on the ability to make accurate shipboard observations and on the question of what degree of exactness might have been accepted as good enough for routine navigational purposes when at sea. (shrink)

This essay examines the problems associated with the installation of a precision instrument at the National Astronomical Observatory of Chile, starting before its construction and following the process through its installation to its later useful life. Between 1908 and 1913, the director of the observatory, Friedrich W. Ristenpart, corresponded with the German manufacturer, A. Repsold & Söhne in Hamburg, trying to identify the critical points pertinent to the installation of the instrument in Chile. These communications reveal how the installation of (...) the instrument required the stabilization of local knowledge (location, adjustment, calibration, and staging) that would allow the data it obtained to be universally validated. This correspondence between user and manufacturer also reveals that the phenomenon of the mobility of instruments implies much more than simply transporting something from one place to another: there is no movement without some type of coordination between the extraction of an object from a certain place and context and its insertion into a new place and set of relationships. (shrink)