3. Augustus De Morgan, Astronomy and Almanacs

Augustus De Morgan never identified himself as an astronomer, and blindness in one eye rendered him unable to make reliable observations with astronomical instruments. Yet he participated actively in the British astronomical community during the mid-nineteenth century, becoming involved as Secretary of the Royal Astronomical Society in major events and controversies that shaped both British and international astronomical practice during the 1840s, and making himself through his writings an authoritative ‘expounder and historian’ of astronomy and its instruments. This chapter revisits De Morgan’s interest in astronomy and his close relationships with leading astronomers of the nineteenth century. It discusses his activities as a writer, arguing that while he raised awareness of history’s forgotten and overlooked astronomers, his publications also reaffirmed the contemporary and historical boundaries of the astronomical community. Finally, it examines De Morgan’s writings about calendrical reforms and an apparent paradox regarding the determination of the date of Easter, to demonstrate how he combined his interests in antiquarianism, ecclesiastical and legal history with his knowledge of mathematics and astronomy to participate in a debate of interest to the wider public.