A Sunspot Catalog by Rafael Carrasco at the Madrid Astronomical Observatory for the Period 1931 – 1933

A sunspot catalog was published by the Madrid Astronomical Observatory from sunspot observations made by Rafael Carrasco and his assistants for the period November 1931 – December 1933. We have digitized this catalog and carried out a quality control to detect inconsistencies. We present a machine-readable version of this sunspot catalog together with an erratum list. Moreover, we compared the Madrid sunspot number and area with other reference series. We found that sunspots in the northern hemisphere were predominant during this period, confirming previous studies. We have also analyzed the group morphological typologies registered in the catalog and show a butterfly diagram drawn with this new information. A comparison with the sunspot catalog by the Royal Greenwich Observatory shows that almost all the groups included in the Carrasco’s catalog are also present in the aforementioned catalog.