elder brother of W. H. Pickering. As director of Harvard College Observatory, he produced a catalogue of brightnesses for 4260 stars, the Harvard Photometry, in 1884, and extended the work in 1908 with the Harvard Revised Photometry. He was an early exponent of astrophotography, and built up an extensive library of photographic plates at Harvard. In 1903 he published the first photographic map of the whole sky. In the 1880s, Pickering began a programme to classify stellar spectra, discovering in the process the first spectroscopic binary, Mizar A. He invented a method for recording several spectra on one plate by placing a large, low-dispersion prism in front of the telescope. The routine work was largely carried out by a team of women assistants, including A. J. Cannon, W. P. Fleming, and Antonia Caetana de Paiva Pereira Maury (1866–1952). The programme yielded the Harvard classification and the Henry Draper Catalogue of stellar spectra.