Fig. 1. CMDs of the star clusters SL 538, NGC 2006, KMHK 1019 and the surrounding field. Note the widening of the main sequence due to Be stars (crosses)

Fig. 2. Colour image made out of B, V, I frames, north up, east to the left. The data have been obtained on 15th December 1992 with EFOSC 2 at the ESO/MPI 2.2 m telescope at La Silla. A 1024 × 1024 pix² coated Thomson THX31156 CCD chip (ESO #19) was used with a pixel scale of 0.34" resulting in a field of view of 5.8' × 5.8'. The frames are centered near NGC 2006 in the upper right part. SL 538 is north of NGC 2006 and to the south-east of this cluster pair a third star cluster is located: KMHK 1019