With the introduction of the new series, we stop the extension of the original series as the new series gives a better number, cleaned from past defects. It turns out that the main defect in the series was the use of weighted counts by the main reference station in Zürich and now Locarno. As such counts were not used for the whole series before 1947, it produced a strong inhomogeneity. As we will now use unweighted counts following the original Wolf definition, it would be impossible to reconcile the newly computed monthly numbers with the original series, which is about 17% too high until May 2015. There would be an artificial step between May and June 2015.
Therefore, the original series is kept accessible to users only for reference when making comparisons with past published studies that used the original sunspot number. So, just like the original Group Number series was never extended beyond 1995, the archived version 1.0 of the Sunspot Number will end in May 2015.BACK