Abstract
Finding a method to determine terrestrial longitude was critical in the early seventeenth century as countries attempted to establish territorial boundaries. The magistrate and natural philosopher Nicolas-Claude Fabri de Peiresc (1580-1637) spent much of his life working on a solution to this problem. As an early technical communicator, he was concerned with the criteria of acceptable observations, the standardization of materials and methods, and the communication of results. He refined a variety of strategies to obtain these observations and ensure their accuracy. He persuaded missionary priests to make observations throughout the Levant by promising patronage and gifts or stressing practical applications in the solution to the problem of longitude and church calendar reform. Although Peiresc did not resolve the issue of determining longitude, his efforts did provide the basis for work by later astronomers.