Czernik 2 and NGC 7554 CCD UBV photometry

We estimated colour-excesses and metallicities separately using (U-B)x(B-V) two-colour diagrams to derive homogeneously determined parameters. The derived E(B-V) colour excess is 0.46+/-0.02mag for Czernik 2 and 0.57+/-0.04mag for NGC 7654. [Fe/H] metallicities were obtained for the first time for both clusters, -0.08+/-0.02dex for Czernik 2 and -0.05+/-0.01dex for NGC 7654.

Keeping the reddening and metallicity as constant quantities, we fitted PARSEC models using Vx(B-V) and Vx(U-B) colour-magnitude diagrams, resulting in estimated distance moduli and ages of the two clusters. We obtained the distance modulus for Czernik 2 as 12.80+/-0.07mag and for NGC 7654 as 13.20+/-0.16mag, which coincide with ages of 1.2+/-0.2 Gyr and 120+/-20Myr, respectively. The distances to the clusters were calculated using the Gaia EDR3 trigonometric parallaxes and compared with the literature.

We found good agreement between the distances obtained in this study and the literature. Present day mass function slopes for both clusters are comparable with the value of Salpeter (1955), being X=-1.37+/-0.24 for Czernik 2 and X=-1.39+/-0.19 for NGC 7654.