Photometry quality parameters of objects in the crowded field (, see Fig. A.1h) vs. magnitudes in B, V, R, Hα, and I passbands. Panels a–e: χ² – a goodness-of-fit parameter, indicating how well an object’s profile is fit by the PSF; panels f–j: sharpness – an object profile’s sharpness with respect to the PSF. The grey dots are stellar objects; cyan circles are contaminants (background galaxies, stellar blends; ) removed from the catalogue based on a visual inspection of HST ACS images; black dots are extended objects that were excluded from further analysis based on their χ² and sharpness. The red lines indicate limits selected for decontamination; objects that fall outside the limits in at least three passbands were excluded. The gradient of the sloping lines is the same in all passbands.