Halley's comet, the first comet whose return was accurately predicted, was
observed by English astronomer Edmund Halley in 1692, when he correctly
estimated the reappearance in 1758, sixteen years after his death as it
turned out. Halley based his calculations on Newton's theory; a long-time
friend of the great scientist, he had paid for the initial printing of
Newton's Principia, collaborating on the section dealing with comets. Over
his eighty-six year lifetime Halley made a number of important
discoveries, which resulted in his appointment as astronomer royal in
1720. The comet that blazons his name across the sky last appeared in
1910.