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

TL;DR

This paper details the long-term sunspot observation and counting procedures at Specola Solare Ticinese in Locarno since 1957, emphasizing its role in maintaining continuity in sunspot number data for solar activity studies.

Contribution

It documents the observational methods and counting rules used at Specola Solare Ticinese, highlighting its role as a pilot station ensuring data consistency since 1957.

Findings

Continuous sunspot data collection since 1957

Standardized counting procedures maintained over decades

Role in international sunspot number calibration

Abstract

Specola Solare Ticinese is an observatory dedicated to Sunspot Number counting, which was constructed in 1957 in Locarno, Southern Switzerland, as an external observing station of the Zurich Federal Observatory. When in 1981 the responsibility of the determination of the International Sunspot Number was assumed by the Royal Observatory of Belgium, 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.