Sunspot Catalogue of the Observatory of the University of Coimbra (1929-1941)

TL;DR

This paper digitizes and analyzes the Coimbra Observatory sunspot catalogue (1929-1941), validating its data against other series to support solar activity research.

Contribution

It provides a machine-readable version of the historical catalogue and compares its data with other sunspot series for validation.

Findings

The catalogue contains reliable sunspot data.

The reconstructed sunspot indices align well with other series.

The data can be used for solar activity studies.

Abstract

A sunspot catalogue was published by the Coimbra Astronomical Observatory (Portugal), now named Geophysical and Astronomical Observatory of the University of Coimbra, for the period 1929-1941. We digitalized data included in that catalogue and provide a machine-readable version. We show the reconstructions for the (total and hemispheric) sunspot number index and sunspot area according to this catalogue, comparing it with the sunspot number index (version 2) and Balmaceda sunspot area series (Balmaceda et al., J. Geophys. Res. 114, A07104, 2009). Moreover, we also compared the Coimbra catalogue with records made at the Royal Greenwich Observatory. The results demonstrate that the historical catalogue compiled by the Coimbra Astronomical Observatory contain reliable sunspot data and therefore can be considered for studies about solar activity.