Rudolphine Tables and instructive examples for computing planetary positions. For most stars these tables were accurate to within one arc minute, and included corrective factors for atmospheric refraction. The tables were sufficiently accurate to predict a transit of Mercury observed by Pierre Gassendi in 1631 and a transit of Venus observed by Jeremiah Horrox in 1639. Rudolphine Tables The Rudolphine Tables () consist of a star catalogue and planetary tables published by Johannes Kepler in 1627, using some observational data collected by Tycho Brahe (1546–1601). The tables are named as "Rudolphine" in memory of Rudolf II, Holy Roman Emperor. Star tables had
Association of Lunar and Planetary Observers Association of Lunar and Planetary Observers The Association of Lunar and Planetary Observers (ALPO or A.L.P.O.) is an international scientific and educational organization established in March, 1947 in the United States by Walter H. Haas, and later incorporated in 1990. ALPO is an organization for advancing and conducting astronomical work by both professional and amateur astronomers who share an interest in solar system observations. It is currently headquartered in Springfield, Illinois. ALPO studies solar system objects such as the Sun, the Earth's Moon, planets, asteroids, meteors, and comets. ALPO stimulates, coordinates, and generally promotes the study of these bodies using