Rediscovery of 23 Historical Records of Naked-Eye Sunspot Observations in AD 1618

Abstract The year 1618 was once regarded as a minimum of the first observed solar cycle or even beginning extended Maunder minimum. However, new results from annual dataset radiocarbon (Usoskin et al., Astron. Astrophys. 649 , A141, 2021) shows that 1620 minimum, instead 1618. We revisited sunspot activity in historical records naked-eye observations (HRNSOs) China, daily telescopic were found on only 28 days 1618, and they are far sufficient to resolve difference. rediscovered 23 HRNSOs by search more than 800 books, with 15 identified independent observations. From here, Chinese had seen several large sunspots On 20 21 June vapor-like so ordinary people could see them thought Sun abnormal. 22 at least three observers reported huge group diffusive, round, object an impressive size. here provide valuable determine Our result confirms one radiocarbon, quite active.