Variations in the Earth's clock error ΔT between AD 300 and 800 as deduced from observations of solar and lunar eclipses

Abstract

Historical observations of solar and lunar eclipses provide the most effective method of tracing fluctuations in the Earth's rate of rotation in the pre-telescopic period. However, the temporal distribution of these data - some of which extend back to 700 BC - is far from uniform. Between AD 300 and 800, no more than about fifty usable observations are preserved. Analysis of these data enables variations in the Earth's clock error, ΔT, to be enumerated with tolerable precision during this interval. It is shown that departures from a parabolic fit are fairly small.