Between 06 Sep 1618 and 25 Sep 1618 a comet was visible to the naked eye.

Evelyn's Diary. 1624. I was not initiated into any rudiments until near four years of age, and then one Frier taught us at the church-porch of Wotton, Surrey [Map]; and I do perfectly remember the great talk and stir about Il Conde Gondomar (age 96), now Ambassador from Spain (for near about this time was the match of our Prince (age 23) with the Infanta (age 17) proposed); and the effects of that comet, 1618, still working in the prodigious revolutions now beginning in Europe, especially in Germany, whose sad commotions sprang from the Bohemians' defection from the Emperor Matthias; upon which quarrel the Swedes broke in, giving umbrage to the rest of the princes, and the whole Christian world cause to deplore it, as never since enjoying perfect tranquillity.