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The biography of Julius Caesar by...Suetonius says that a comet was seen over Rome just after the assassination of Caesar in 44BC, which was believed to be his soul ascending to heaven.
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William the Conqueror saw a bright comet, which we now know to be Halley's comet, in 1066. This was perceived by King Harold as a dire omen, but as a favourable one by William. Indeed, William's battle cry came: 'A new star, a new King'. Several months later, Harold was indeed killed at the Battle of Hastings and William had an image of the comet embroidered in the Bayeux Tapestry. A group of terrified Saxons is seen looking up at it; a legend reads, 'They are in awe of the stars.'