Tilt angle histogram of the Schwabe data for group centres within 60° central meridian distance and polarity separations Δβ> 3°. In this analysis, only spots with umbral areas of 5 MSH or more were used to compute the weighted positions of the polarities. The selection therefore affects both tilt angles and polarity separations. As compared with the hatched bars in Fig. 11, many groups have now turned into unipolar groups, since one of the polarities was represented by a single spot of less than 5 MSH.