Historical evidence concerning the Sun: interpretation of sunspot records during the telescopic and pretelescopic eras

Abstract
The value of sunspot observations in investigating solar activity trends - mainly on the centennial to millennial timescale — is considered in some detail. It is shown that although observations made since the mid-eighteenth century are in general very reliable indicators of solar activity, older data are of dubious quality and utility. The sunspot record in both the pretelescopic and early telescopic periods appears to be confused by serious data artefacts.