  Catalogues of sunspots have been available with useful information about
sunspots or sunspot groups for approximately the last 150 years. However, the
task of merging these catalogues is not simple. In this paper, a method is
suggested of converting the types of sunspot groups that were proposed by
Cortie (1901) into the well-known Zurich types of sunspot groups. To achieve
this, the sunspot catalogue of the Valencia University Observatory (from 1920
to 1928) was used in addition to the descriptions proposed by Cortie. To assess
the quality of this conversion scheme, the Zurich type was computed from the
Valencia catalogue, and the resulting contribution of each group type was
compared to what can be found in other catalogues. The results show that the
proposed scheme works well within the errors that are found in the different
catalogues.

Solar and Stellar Astrophysics