χ² estimate as a function of age for three representative clusters: ESO 92-18, Patchick 125, and Patchick 126. The colour of the lines depends on the metallicity, specified in the legend. The black dashed lines indicate the minimum χ² value at the relative age. The age and metallicity that correspond to the are listed in Table 3. Right panel: Gaia EDR3 CMD for ESO 92-18. The PARSEC isochrone (black dotted line) was fit using the age and metallicity obtained by the χ² analysis and listed in Table 3. The reddening, distance modulus, and extinction are listed in Table 2.