AAVSO

Founded in 1911, the American Association of Variable Star Observers has collected and cataloged over 34 million variable star observations. Most stars do not stay the same brightness. By observing and recording a star’s brightness over time, much can be learned about the star. The observations are primarily contributed by amateur astronomers but the online database of observations is routinely accessed by professional astronomers. Several times a year professional astronomers request specific observations by AAVSO members.