Forty two years counting spots: solar observations by D. E. Hadden during 1890-1931 revisited

TL;DR

This paper revisits and digitizes D. E. Hadden's sunspot observations from 1890-1931, analyzing them against standard series and revealing new details on significant historical sunspot groups affecting space weather.

Contribution

The study recovers and digitizes Hadden's historical sunspot data, providing new insights into two major sunspot groups and their space weather impacts.

Findings

Hadden's data aligns with standard sunspot series

Identification of two significant sunspot groups in 1892 and 1898

New details on historical space weather events

Abstract

We have recovered the sunspot observations made by David E. Hadden during 1890-1931 from Alta, Iowa. We have digitized the available data published by Hadden in different astronomical journals. This data series have been analyzed and compared with the standard sunspot number series. Moreover, we provide additional information on two great sunspot groups, previously not described, that originated two important extreme episodes of space weather on February 1892 and September 1898.