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 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 methods and instruments available within the communities of both amateur and professional astronomers.
ALPO had no initial formal structure but later found it necessary to specialize as its membership chose to narrow their studies to certain favored observed celestial objects.
ALPO adopted a similar structure with sections like that of the British Astronomical Association (BAA) in order to properly study the objects observed.
ALPO publishes a quarterly periodical, The Strolling Astronomer - The Journal of the Association of Lunar and Planetary Observers (ISSN 0039-2502, OCLC 1766616) since 1947, referred to by abbreviation as both StAst and JALPO.