Number of Sunspot Groups from the Galileo-Scheiner controversy revisited

Abstract

We revise the sunspot observations made by Galileo Galilei and Christoph Scheiner in the context of their controversy on the nature of sunspots. Their sunspot records not included in the current sunspot group database, used as a basis to calculate the sunspot group number, are analyzed. Within the documentary sources consulted in this work, we can highlight the sunspot observations by Scheiner included in the letters sent under the pseudonym Apelles to Marcus Welser and the first sunspot observations made by Galileo, which can be consulted in Le opere di Galileo Galilei. These sunspot observations would extend the temporal coverage for these two observers and filling some gaps in the current group database in the earliest period where the data available is sparse. Moreover, we have detected changes in the quality of the sunspot drawings made by Galileo and Scheiner in their observation series affecting to the number of groups recorded by the two observers. We also compare these records with sunspot observations made by other astronomers of that time. According to this comparison and regarding the same observation days, Scheiner was generally the astronomer who reported more sunspot groups while Harriot, Cigoli, and Galileo recorded a similar number of groups. We conclude these differences are mainly because of the observational method used by the observers.

References in corpus (4)

• Visualization of the challenges and limitations of the long-term sunspot number record
• Sunspot positions, areas, and group tilt angles for 1611-1631 from observations by Christoph Scheiner
• Sunspot characteristics at the onset of the Maunder Minimum based on the observations of Hevelius
• Sunspot observations by Charles Malapert during the period 1618-1626: a key dataset to understand solar activity before the Maunder minimum

Cited by in corpus (4)

• Re-calibration of the Sunspot Number: Status Report
• Revisiting Christoph Scheiner's Sunspot Records: a New Perspective on Solar Activity of the Early Telescopic Era
• Daniel Mögling's sunspot observations in 1626 - 1629: A manuscript reference for the solar activity before the Maunder Minimum
• Comparison of solar activity proxies: eigen vectors versus averaged sunspot numbers