Historical astronomy is the science of analysing historic astronomical data. The American Astronomical Society (AAS), established 1899, states that its Historical Astronomy Division "...shall exist for the purpose of advancing interest in topics relating to the historical nature of astronomy. By historical astronomy we include the history of astronomy; what has come to be known as archaeoastronomy; and the application of historical records to modern astrophysical problems." [1] Historical and ancient observations are used to track theoretically long term trends, such as eclipse patterns and the velocity of nebular clouds. [2] Conversely, using known and well documented phenomenological activity, historical astronomers apply computer models to verify the validity of ancient observations, as well as dating such observations and documents which would otherwise be unknown.