Astronomical observations in the Irish annals and their motivation

The astronomical entries in the Irish annals have been examined in a serious astronomical context by R. R. Newton as part of his research into the accelerations of the earth and moon, and by D. Schove and A. Fletcher as part of the Spectrum of Time project. They have never, however, been fully collated and examined as a whole as this paper undertakes to do. What emerges is a body of records from 442 to 1133 documenting eclipses, comets, aurorae, volcanic dust clouds, and possibly a supernova; from 627 to 1133 all of these records are of observations made in or near Ireland, and most of them are accurate in their chronological and descriptive details. Analysis of the details of these records implies that at least from the seventh to the eleventh centuries careful and sustained observation and recording of astronomical phenomena was conducted in some Irish monasteries and it is clear that the underlying motive was religious and specifically eschatological, viz. to detect the first signs of the end of time as prognosticated in the Book of Revelation. Critical examination of these data throws new light on the circumstances of the Synod of Whitby in 664, establishes the date of the eruption of the volcano Eldgjá in Iceland as springtime of 939, and identifies a possible Western observation of the supernova of 1054.