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. Today with
members in 46 countries, and headquarters in Cambridge, Massachusetts, USA,
it is the world's largest association of variable star observers.
The AAVSO coordinates, evaluates, compiles, processes, publishes, and
disseminates variable star observations to the astronomical community
throughout the world. The archives of the AAVSO currently contain over 9
million observations. Approximately 575 observers from around the world send
over 300,000 observations each year. At the end of each month, incoming
observations are sorted by observer and checked for errors. They are
converted into computer readable form and processed using computer systems
at AAVSO Headquarters. These observations are then added to the data files
for each star in the AAVSO International Database. This database is a
tribute to the skill, enthusiastic devotion, and dedication of AAVSO
observers since 1911.
YOU can contribute significantly to the study of variable stars by making
only a few hours of observations each month!
A telescope of any size or a pair of binoculars is sufficient equipment.
Long training and special skills are not necessary to begin variable star
observing. As long as you take care to follow instructions, you can be
making good observations after a few weeks of practice.
Beginning visual observers usually start with long period and semiregular
variables. The large amplitudes and slow rates of variation of these stars
make their observation an ideal means for observers to become experienced at
making brightness estimates.
As observers gain experience, they often add to their programs other types
of variable stars--cataclysmic variables, symbiotic stars, and R Coronae
Borealis stars. These stars vary unpredictably, and--depending on their state
of behavior--may require very frequent observations.
Some observers focus on eclipsing binaries or RR Lyrae stars. Observing
these stars requires additional preplanning and special observing
Observers may also include in their programs systematic, regular searches
for novae or supernovae
Once you begin, you will be sending your observations monthly to AAVSO
Headquarters on special "report forms" by mail, fax, or electronically
Each year the AAVSO publishes the names of observers and the annual total
of their observations in the
Journal of the AAVSO
There is no minimum monthly observation quota--even ONE observation is
useful and significant!
Benefits of Membership
Members receive all the information and material
needed to establish their own variable star observing program, subscriptions
Journal of the AAVSO
, and may choose from a
large number of other publications available free of charge to members.
Also, members receive notices of the semi-annual meetings of the AAVSO which
they are encouraged to attend, and other mailings.
Services to the Observer
Gerry Dyck, AAVSO Member-Observer and Music Teacher, at his home-made telescope
The AAVSO enables variable star observers to
contribute vitally to variable star astronomy by accepting their
observations, incorporating them into the AAVSO data files, publishing them,
and making them available to the professional astronomer. Incorporating an
observer's observations into the AAVSO archives means that future
researchers will have access to those observations, so the observer is
contributing to the science of the future as well as the present. Also, the
AAVSO coordinates observing runs between professional and amateur
astronomers, in which observations from amateur astronomers play an
important role in correlating observations obtained with special instruments
at earth-based observatories or on board satellites.
Upon request, the AAVSO will help set up an appropriate observing program
for an individual, an astronomy club, an elementary school, high school, or
college, etc. In this way observers, students, and faculty are able to make
the best use of their resources and to do valuable science. The AAVSO can
also assist in teaching observing techniques and in suggesting stars to be
included in a program.
Services to the Astronomical Community
AAVSO data, both published and unpublished, are made available to astronomers
around the world. AAVSO
services are sought by astronomers for:
Real-time, up-to-date information on unusual stellar activity;
Assistance in scheduling and executing of variable star observing programs
using earth-based large telescopes and instruments on board satellites;
Assistance in simultaneous optical observations of program stars and
immediate notification of their activity during earth-based or satellite
Correlation of AAVSO optical data with spectroscopic, photometric, and
polarimetric multi-wavelength data;
Collaborative statistical analysis of stellar behavior using long-term
Collaboration between the AAVSO and professional astronomers for real-time
information or simultaneous optical observations has enabled the successful
execution of many observing programs, particularly those using satellites. A
significant number of rare events have been observed with these satellites
as a result of timely notification by the AAVSO.
Services in Education
Tal Mentall of the Amateur Telescope Makers of Boston introduces youngsters to
astronomy through the AAVSO
Partnership in Astronomy
For many years the AAVSO has been a source of
information and guidance to students who decide to study variable stars for
class or science fair projects. The AAVSO's most recent project in education
is Hands-On Astrophysics--a curriculum for high school and college science
and math classes which uses the AAVSO's unique variable star database. Also,
its Mentorship Program connects experienced and enthusiastic variable star
observers with anyone in their vicinity who is interested in learning how to
become a better observer.
AAVSO Observing Programs
Most AAVSO observations are made visually. Stars best suited for
visual observation have amplitudes of variation of more than one magnitude.
The limiting magnitude of observations is 16.5 and the accuracy of the data
is between ±0.2 and ±0.4 magnitude. The AAVSO Visual Observing
includes about 3600 variable stars.
Stars with small variations can be observed
photoelectrically. The AAVSO Photoelectric Observing Program contains 50
bright, mostly red variables with less than 1 magnitude of variation. The
photoelectric and the visual observing programs complement each other since
most of these stars are also in the visual observing program. The accuracy
of photoelectirc observations is ±0.008 magnitude.
Charge-Coupled Device (CCD):
The minima of faint variables can be observed
even with a small telescope equipped with a CCD. The CCD observing program
consists of mostly long period variables in the visual program. Faint CCD
observations complement both of the other observing programs of the AAVSO.
Divisions and Committees
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
AAVSO Headquarters, under the authority of the AAVSO Director. These
committees and divisions are:
Eclipsing Binary Stars
RR Lyrae Stars
In addition, there is a New Charts Committee to oversee the preparation of
new variable star charts and a Telescope Committee that is responsible for
receiving and selling telescopes donated to the AAVSO. The Chairs of these
An AAVSO light curve of the variable star SS Cygni.
Membership in the AAVSO is open to anyone interested in variable stars and
in contributing to the support of valuable research. Research on variable
stars is important because it can provide much information--mass, radius,
internal and external structure, composition, temperature and
luminosity--about the properties of these stars. This information can then
be extrapolated to other types of stars, including our Sun.
Amateur astronomers are making a real and useful contribution to science by
observing variable stars and submitting their observations to the AAVSO
International Database. They have both time and ready access to observing
instruments needed to gather data on the brightness changes of thousands of
In addition to contributing valuable observations, you can support the work
carried on at Headquarters through your annual membership dues.
To become a member, or to obtain more information, please contact:
25 Birch Street
Cambridge, MA 02138
Phone: 617-354-0484 Fax: 617-354-0665
Visit the AAVSO web site at
http://www.aavso.org and visit the AAVSO Hands-On Astrophysics
website at http://hoa.aavso.org
to The Amateur Scientist