Solar Physics

, Volume 291, Issue 9–10, pp 3075–3080 | Cite as

Sunspot Observations and Counting at Specola Solare Ticinese in Locarno Since 1957

  • Sergio Cortesi
  • Marco Cagnotti
  • Michele BiandaEmail author
  • Renzo Ramelli
  • Andrea Manna
Sunspot Number Recalibration


Specola Solare Ticinese is an observatory dedicated to sunspot number counting. It was constructed in 1957 in Locarno, Southern Switzerland, as an external observing station of the Zurich Federal Observatory. When the responsibility of the determination of the International Sunspot Number was assumed by the Royal Observatory of Belgium in 1981, Specola Solare Ticinese was given the role of pilot station, with the aim of preserving the continuity in the counting method. We report the observing procedure and counting rules applied in Locarno.


Sunspots, statistics Solar Cycle, observations 



The association ASST organizes the financing of Specola Solare Ticinese and was established by Alessandro Rima (who directed it from 1980 until 1991) and Paul Utermohlen. Jan Olof Stenflo at ETHZ recommended using Specola Solare Ticinese as the pilot station for SIDC in Brussels. Since 1992, ASST has been directed by Philippe Jetzer. Specola Solare Ticinese is mainly financed by the Ticino Canton through the Swisslos found. We thank Mario Gatti for helpful discussions.

Disclosure of Potential Conflicts of Interest

The authors declare that they have no conflicts of interest.


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Copyright information

© Springer Science+Business Media Dordrecht 2016

Authors and Affiliations

  • Sergio Cortesi
    • 1
  • Marco Cagnotti
    • 1
  • Michele Bianda
    • 2
    Email author
  • Renzo Ramelli
    • 2
  • Andrea Manna
    • 1
  1. 1.Specola Solare TicineseLocarnoSwitzerland
  2. 2.Istituto Ricerche Solari LocarnoLocarno-MontiSwitzerland

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