sunspots
Monthly Mean Relative Sunspot Numbers
Description
The monthly means of daily relative sunspot numbers,
which are based upon counts of spots and groups of spots.
D. F. Andrews and A. M. Herzberg,
Data: A Collection of Problems from Many Fields for the Student and Research Worker,
Springer-Verlag, New York, 1985.
The data was previously collected from different observers by the
Swiss Federal Observatory, Zurich, Prof. M. Waldmeier, Director.
M. Waldmeier,
The Sunspot Activity in the Years 1610-1960,
Schulthess, Zurich, 1961.
The data is currently collected by the Tokyo Astronomical Observatory,
Tokyo, Japan.