Solar Physics

, Volume 291, Issue 9–10, pp 2487–2492 | Cite as

Transition of the Sunspot Number from Zurich to Brussels in 1980: A Personal Perspective

  • J. O. StenfloEmail author
Sunspot Number Recalibration


The Swiss Federal Observatory, which had been founded in 1863 by Rudolf Wolf, was dissolved in connection with the retirement of Max Waldmeier in 1979. The determination of the Zurich sunpot number, which had been a cornerstone activity of the observatory, was then discontinued by ETH Zurich. A smooth transition of the responsibility for the sunspot number from Zurich to Brussels was achieved in 1980, however, through which it was possible to avoid a discontinuity in this important time series. Here we describe the circumstances that led to the termination in Zurich, how Brussels was chosen for the succession, and how the transfer was accomplished.


Sunspots, Statistics Solar Cycle, Observations 


  1. Shapley, A.H.: 1979. Internal study for IAU Comm. 10, reported in a letter of 15 May 1979. Google Scholar
  2. Waldmeier, M.: 1979, Tätigkeitsbericht der Eidgenössischen Sternwarte Zürich für das Jahr 1978/79, ETH, Zurich. Google Scholar

Copyright information

© Springer Science+Business Media Dordrecht 2016

Authors and Affiliations

  1. 1.Institute for AstronomyETH ZurichZurichSwitzerland
  2. 2.Istituto Ricerche Solari LocarnoLocarno-MontiSwitzerland

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