8. The CM diagrams of the clusters

From the CM diagrams in Figs. 13 (click here)-16 (click here), the following inferences can be drawn:

(i)

 The photoelectric data merge smoothly with the CCD observations, indicating that there are no systematic differences in the calibrations.

(ii)

 In all the star clusters under discussion, an evolutionary effect is clearly visible in the upper part of the cluster MS. In NGC 5662 and NGC 6087, a few proper motion cluster members have reached the giant phase of stellar evolution.

(iii)

 Well defined cluster main-sequences extending from to +3.0 in NGC 4103; from to +4 in NGC 5662 and from to +4 in NGC 6087 are clearly seen. Such a long sequence is not present in NGC 3228 (Fig. 13 (click here)). In fact very few cluster members seems to exist in the present sample of CCD data. It could be due to the fact that imaged regions are located almost at the edge of the cluster diameter (see Table 4 (click here)).

(iv)

 It is clear that below , the luminosity functions of the clusters do not rise steeply enough to dominate the field star contamination. In this region, the present observations are unable to separate unambiguously cluster members from the field stars.