Sunspot Numbers and Areas from the Madrid Astronomical Observatory (1876-1986)

Abstract

The solar program of the Astronomical Observatory of Madrid started in 1876. For ten solar cycles, observations were made in this institution to determine sunspot numbers and areas. The program was completed in 1986. The resulting data have been published in various Spanish scientific publications. The metadata allowed four periods of this program (with different observers and instruments) to be identified. In the present work, the published data were retrieved and digitized. Their subsequent analysis showed that most of these data can be considered reliable given their very high correlation with international reference indices (International Sunspot Number, Group Sunspot Number, and Sunspot Area). An abrupt change emerged in the spots/groups ratio in 1946 which lasted until 1972.

27 pages, 10 figures, accepted for publication in Solar Physics

References in corpus (1)

• Historical Sunspot Observations: A Review

Cited by in corpus (6)

• Updated sunspot group number reconstruction for 1749-1996 using the active day fraction method
• Iwahashi Zenbei's Sunspot Drawings in 1793 in Japan
• Dependence of the Sunspot-group Size on the Level of Solar Activity and its Influence on the Calibration of Solar Observers
• Equivalence relations between the Cortie and Zurich sunspot group morphological classifications
• Eric Strach: four decades of detailed synoptic solar observations (1969-2008)
• Comparison of automatic methods to detect sunspots in the Coimbra Observatory spectroheliograms