784 Pickeringia (prov. designation: or ) is a large background asteroid, approximately in diameter, located in the outer region of the asteroid belt. It was discovered on 20 March 1914, by American astronomer Joel Hastings Metcalf at the Winchester Observatory in Massachusetts. The dark C-type asteroid has a rotation period of 13.1 hours and an irregular shape. It was named after American astronomers Edward Charles Pickering (1846–1919) and his brother William Henry Pickering (1858–1938). Orbit and classification Pickeringia is a non-family asteroid of the main belt's background population when applying the hierarchical clustering method to its proper orbital elements. It orbits the Sun in the outer asteroid belt at a distance of 2.3–3.8 AU once every 5 years and 5 months (1,989 days; semi-major axis of 3.1 AU). Its orbit has an eccentricity of 0.24 and an inclination of 12° with respect to the ecliptic. The body's observation arc begins at Heidelberg Observatory on 30 September 1921, more than seven years after its official discovery observation at Winchester Observatory . Naming This minor planet was named after American astronomers Edward Charles Pickering (1846–1919) and his brother William Henry Pickering (1858–1938), who were the directors of the Harvard Observatory and the Boyden Station at Arequipa, respectively. William Henry also discovered Phoebe, an irregular moon of Saturn. The was mentioned in The Names of the Minor Planets by Paul Herget in 1955 (). The lunar crater Pickering and the Martian crater Pickering were also named in honor of the two astronomers. Physical characteristics In the Bus–Binzel SMASS classification, Pickeringia is a common, carbonaceous C-type asteroid. Rotation period In January 2017, a rotational lightcurve of Pickeringia was obtained from photometric observations by the Spanish group of asteroids observers (OBAS). Lightcurve analysis gave a rotation period of hours with a brightness variation of magnitude (). The result supersedes observations taken during the 1990s by European astronomers using the ESO 0.5-metre telescope at La Silla Observatory, Chile, which gave a period of hours with an amplitude of magnitude (). as well as a period determination by French amateur astronomer Laurent Bernasconi in December 2004, which gave and an amplitude of magnitude (). Modeled lightcurve Two modeled lightcurves, published by Josef Ďurech and Josef Hanuš in 2016, using photometric data from the Lowell Photometric Database (LPD) and other sources, gave a sidereal period of and , respectively. Each modeled lightcurve also determined two spin axes of