As shown in Figures 1, 2, and 3, we can see that the main shapes of the CMDs of star clusters
are reproduced well. Therefore, the properties of star clusters derived from the CMD fitting are
reliable. In detail, the stellar ages, metallicities, distances, and reddenings determined by comparing
observational CMDs to synthetic CMDs are listed in Table 1. It shows that these clusters have a
minimum age of 4 Gyr and a maximum age of 13 Gyr, with an average of 11.42 Gyr. The lowest and
highest metallicities (Z) of these globular clusters are 0.0001 and 0.01, respectively, with an average
of 0.00145. As a whole, the results show old ages and poor metallicities for globular clusters. This
is in agreement with most previous studies.