On 11 January 1672, the Fellows of the British Royal Society were treated to a demonstration of Isaac Newton’s reflecting telescope, which formed images with mirrors rather than with the lenses that had been used since the time of Galileo. Afterward, the fellows hailed Newton as the inventor of this marvelous new instrument, an attribution that sticks to the present. However, this linear historical account obscures a far more interesting, convoluted story. Newton’s claim was immediately challenged on behalf of two other contenders, James Gregory, and Laurent Cassegrain. More confounding, the earliest known concept of using a curved mirror to focus light predated Newton by more than 1,500 years; the final realisation of a practical reflecting telescope post-dated him by more than a half century.