Eclipses have been perceived as peculiarly portentous events. The ability to predict their occurrence has been an important one throughout history. Stonehenge may well have been built for this very purpose, and the ancient Babylonians, Egyptians and Greeks all set great store by keeping accurate records of these heavenly phenomena. Christopher Columbus used his knowledge of an eclipse on Feb. 29, 1504, to convince native Americans that God was angry with them. The eclipse of 1919 was used to prove part of Einstein's theory of relativity. The cyclical pattern which eclipses follow was calculated thousands of years ago, but only with the advent of computers has it been possible to analyze it fully. An eclipse provides many unique research opportunities.