... A wordlwide network of amateur and professional astronomers record and time the mutual eclipses and occultations of the Galilean satellites as accurately as possible. ... Already, the acceleration of Io is evident in the data and continued monitoring through this coming season will help pin down the acceleration of the other three satellites. ... From Dr Apostolos Christou, Armagh Observatory: . ... If you want to know the observing times from your location get it by filling in this form . ...