Sidereal Messages: Print Letters in Restoration Astronomical Writing

Abstract Astronomy, a paradigmatic observational discipline of early modern ‘science’, relied on epistolary communication for coordinating practitioners across the world, publishing discoveries and theories, and seeking their confirmation from other virtuosi. Epistolary form ‘travelled’ from an individual exchange between scholars, via the print publication of such letters for the benefit of a wider readership, to the framing of bespoke isagogic textbooks. This article explores the affordances of Restoration printed astronomical letters, contrasting their performance of familiarity between sender and recipient with the public nature of the communication. By reference to letters published in the Philosophical Transactions , individual print letters, and letter‐books, including Christiaan Huygens's Cosmotheoros , the article shows how each type utilizes the familiar and the formal aspects of the letter form differently. The print letter emerges as a form uniquely suited for performing individual authority and fashioning an expert community, as well as communicating expert knowledge to non‐specialists.