- American Association Of Variable Star Observers (AAVSO) - Professional and Amateur collection, research, and analysis of variable star observations.
- American Astronomical Society (AAS) - Established 1899, AAS is the major professional organization in North America for astronomers, other scientists and individuals interested in astronomy.
- Association of Lunar and Planetary Observers - A medium for advancing and conducting work by both professional and amateur astronomers who share an interest in Solar System observations. Includes publications, programs, and image archive.
- Astronomical Society of the Pacific - Disseminates astronomical information. The ASP has become the largest general astronomy society in the world, with members from over 70 nations.
- European Association for Astronomy Education - Improves and promotes astronomical education at all levels in all institutions involved in teaching astronomy in Europe. Contains membership information, the group's history, news, newsletters and projects.
- European Astronomical Society (EAS) - An association founded under the Swiss Civil Code in 1990. Its purpose is to contribute to and promote the advancement of astronomy in Europe.
- International Association of Geodesy - Member information, meeting announcements, publications and reports, awards, and links to related sites.
- International Earth Rotation Service (IERS) - Works to maintain the International Celestial Reference System and Frame, and the International Terrestrial Reference System and Frame, and to provide timely and accurate data on the Earth's orientation for current use and long-term studies. Site describes the group's structure and function.
- International Occultation Timing Association (IOTA) - Established to encourage and facilitate the observation of occultations and eclipses. It provides predictions for grazing occultations of stars by the moon and predictions for occultations of stars by asteroids and planets, information on observing equipment and techniques, and reports to the members of observations made.
- International Occultation Timing Association: European Section (IOTA/ES) - A project consisting of predictions and data for the moon, asteroids, and planets.
- International Organisations for Archaeoastronomy and Cultural Astronomy - Provides general information for the European Society for Astronomy in Culture and International Society for Archaeoastronomy and Astronomy in Culture.
- Joint Organization for Solar Observations (JOSO) - Facilitates collaboration in solar physics among European solar astronomers. Contains details about JOSO's aims, structure, meetings and working groups.
- Night Sky Live - A network of volunteers have cameras focused on the sky to create a 360 degree map of the planets and stars at one time. Data is fed into a computer and filtered for atmospheric interference. Page includes details of the procedure, as well as a discussion forum.
- Royal Astronomical Society of Canada - Key activities include research and observing planets, stars, celestial phenomena and the abatement of light pollution.
- Scientific Committee on Solar-Terrestrial Physics - Promotes international interdisciplinary programs in solar-terrestrial physics, and organizes and coordinates such programs. Site has a newsletter, meetings and events, member directory, announcements, and links to related groups.
- The Astronomical League - Composed of over two hundred local amateur astronomical societies from across the United States. Information on national conventions (ALCons), member societies, regions, Atronomy Day, and awards.
- The Astronomical Society of South Australia - Founded in 1892, is the oldest society of its kind in Australia. Its objectives are to promote the Science of Astronomy and all its branches by holding regular meetings and viewing nights, circulating current astronomical information, and encouraging popular interest.
- The International Astronomical Union (IAU) - Founded in 1919, has a mission to promote and safeguard the science of astronomy through international cooperation. The organization is also the internationally recognized authority for assigning designations to celestial bodies and surface features on such bodies.
- The Planetary Society - A nonprofit organization that promotes exploration of the solar system and the search for extraterrestrial intelligence.
- The Webb Society - An international society of amateurs and professionals specialising in the observation of double stars and deep sky objects, founded in 1967.
- Utah Skies - Information useful and interesting to amateur astronomers, especially those located in Utah. Includes events, news, data and reference materials, and a weekly viewing conditions forecast. Has a special section about light pollution.
