Dynamical age in logarithmic units (color-coded) as a function of stellar mass and angular resolution (milliarcsecond, mas), for a 5 Myr-old star cluster placed at z = 6 and observed at tangential magnification μ_T = 10. The solid black curve marks the locus of Π = 1 separating bound (Π >  1) from unbound (Π <  1) systems. The cases of HST (1 pixel, 30 mas), VLT/MAVIS with an expected FWHM of 20 mas and E-ELT/MAORY-MICADO with FWHM of 10 mas are shown. VLT/MAVIS and E-ELT/MAORY-MICADO can probe star clusters down to a few 10⁵ M_⊙, provided that the S/N and the knowledge of the PSF allow a proper morphological analysis and/or PSF deconvolution. The slope of the Π = 1 curve flattens if the magnification and/or the age of the system increase (dotted curve). UV apparent magnitudes at 1500 Å, corresponding to 2, 1 and 0.5 × 10⁶ M_⊙ objects, are indicated as horizontal white dotted lines.