Fitting results for NGC 1850 using isochrone-clouds with Z = 0.006, leading to age of ∼185 Myr. Left: observed stars in NGC 1850 without Hα emission, colour-coded according to the ratio of the convective core mass versus total stellar mass. Middle: observed stars in NGC 1850 with Hα emission colour-coded according to convective core mass. The isochrone with minimum amount of mixing at 185 Myr is plotted in magenta for reference in both panels. Right: distribution of the fitted core mass as a fraction of total stellar mass, indicated in black for the full sample, in dashed blue for stars without Hα emission and in dashed-dotted red for stars with Hα emission. The distribution of fractional core mass for the 185 Myr isochrone with minimum mixing is shown in dotted magenta.