AAVSO Vision:
The AAVSO seeks to be the world-recognized leader in information and data on variable stars.

AAVSO Mission:
The AAVSO is an international non-profit organization of variable star observers whose mission is: to observe and analyze variable stars; to collect and archive observations for worldwide access; and to forge strong collaborations and mentoring between amateurs and professionals that promote both scientific research and education on variable sources.

The American Association of Variable Star Observers (AAVSO) is a non-profit worldwide scientific and educational organization of amateur and professional astronomers who are interested in stars that change in brightness — variable stars.

The AAVSO was founded in 1911 at Harvard College Observatory to coordinate variable star observations made largely by amateur astronomers. In 1954, the AAVSO became an independent, private research organization headquartered in Cambridge, Massachusetts. Today, with members in 45 countries and over 14.5 million observations, the AAVSO is the world's largest association of variable star observers.

Membership in the AAVSO is open to anyone — professionals, amateurs, and educators alike — interested in variable stars and in contributing to the support of valuable research. Professional astronomers have neither the time nor the telescopes needed to gather data on the brightness changes of thousands of variables, and amateurs make a real and useful contribution to science by observing variable stars and submitting their observations to the AAVSO International Database.

In addition to the valuable observations that members make, their annual dues support the work carried on at headquarters. Please visit our membership pages for more information on how you can contribute to the science of astronomy and to explore the profiles of our observers/members. Or check out Frappr (friend mapper) to see where our observers are located around the globe!

What We Do

Pro-Am Collaboration and the AAVSO - article by AAVSO Director, Arne Henden, about the AAVSO and the valuable professional-amateur collaboration that we foster. ASP Conference Series, 2006. Article is pdf format (1.4 MB).

The AAVSO coordinates, evaluates, compiles, processes, publishes, and disseminates variable star observations to the astronomical community throughout the world.

Observers send their data to Headquarters electronically or via postal mail where they are checked, processed and added to the AAVSO International Database. Once the data have been validated at headquarters, they become available through the AAVSO website. Special requests can also be made to AAVSO Headquarters directly. The AAVSO and its observers frequently provide the professional community with archival data, intensive monitoring of interesting variable stars, and even target-of-opportunity event notification for coordinated observing campaigns and satellite observations.

Members and observers have a unique opportunity to present and exchange ideas at the AAVSO meetings. The AAVSO organizes two meetings a year, one in the fall and one in the spring. The fall meeting is the official AAVSO annual meeting that is always held near the AAVSO headquarters in Cambridge, MA. The spring meeting is held outside of the state of Massachusetts with the intention of attracting more members and observers to attend. Anyone interested in the AAVSO and its activities are invited and encouraged to participate in these exciting events.

AAVSO publications provide the global community with valuable observing information. The type of published information is diverse, ranging from Dr. Dorrit Hoffleit's book entitled Women in the History of Variable Star Astronomy to the bi-annual publication of The Journal of the AAVSO, a collection of scientific papers that focuses on variable stars.

Observations of most types of variable stars are coordinated and published by the Director and the technical staff at AAVSO Headquarters. Observing for certain types of stars is coordinated outside of AAVSO Headquarters, under the authority of the AAVSO Director. More information on these committees and divisions may be found in the Observing Programs section of this website.

The AAVSO has an active Mentor Program that is available to any observer who is wishing for a little guidance.