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Point Spread Function (PSF) photometry of open star clusters Melotte 72 and NGC 2158 was performed using g and r band data from the Sloan digital Sky Survey (SDSS) Data Release 7. Instrumental magnitudes of stars in both bands were transformed into calibrated magnitudes using standard equation. Color-Magnitude (CM) diagrams were produced and compared with the SDSS isochrones for AB stellar system for different ages and/or metallicities. The objective of this study was to determine the physical parameters (age, distance, metallicity, reddening) of open clusters from CM diagrams. The best fit isochrones were used to estimate cluster parameters. The observed parameters were then compared with the WEBDA data base. KEYWORDS: PSF Photometry, Melotte 72, SDSS, NGC 2158, Isochrone Fitting, IRAF