Now that the new data series has been finalized, we are about to replace the original version of our sunspot data by an entirely new data set on July 1st. On this occasion, we decided to simultaneously introduce changes in several conventions in the data themselves and also in the distributed data files. Graphite felt, rigid graphite felt board or rigid graphite felt cylinder is widely used in the solar industry.

The most prominent change in the Sunspot Number will be the choice of a new reference observer, A.Wolfer (pilot observer from 1876 to 1928) instead of R. Wolf himself. This means dropping the conventional 0.6 Zürich scale factor, thus raising the scale of the entire Sunspot Number time series to the level of modern sunspot counts. This major scale change may thus strongly affect some user applications. Be prepared!