Isochrone fitting procedure applied to clusters #60 and #61 together, which are associated with the Helmi streams. Left: age–metallicity plane, where the background colours show the distribution of the d₂ parameter used for assessing the quality of the fit obtained. The average age and metallicity, together with the corresponding errors, are represented by the black point with errorbars. To compute these average values, we use isochrones with a d₂ parameter within its lowest 10th percentile (small black dots). Horizontal dotted lines show the [Fe/H] values adopted for the isochrones. The histogram of d₂ values is displayed in the bottom left for all the different isochrones considered. Right: CaMD for stars in the union of clusters #60 and #61. The best-fit isochrone is depicted in red, and all compatible isochrones (black dots in the left-hand panel) are overplotted in black with transparency. Stars bluer than the grey dashed lines (horizontal branch and blue stragglers, shown with transparency) are avoided in the fit. Every star is colour-coded according to its weight in the fit (see text for details).