  The unprecedented sensitivity and spatial resolution of next generation
ground-based extremely large telescopes (ELTs) will open a completely new
window on the study of resolved stellar populations. In this paper we study the
feasibility of the analysis of nuclear star cluster (NSC) stellar populations
with ELTs. To date, NSC stellar population studies are based on the properties
of their integrated light. NSC are in fact observed as unresolved sources even
with the HST. We explore the possibility to obtain direct estimates of the age
of NSC stellar populations from photometry of main-sequence turn-off stars. We
simulated ELT observations of NSCs at different distances and with different
stellar populations. Photometric measurements on each simulated image were
analysed in detail and results about photometric accuracy and completeness are
reported here. We found that the main-sequence turn-off is detectable -and
therefore the age of stellar populations can be directly estimated- up to 2Mpc
for old, up to 3 Mpc for intermediate-age and up to 4-5 Mpc for young stellar
populations. We found that for this particular science case the performances of
TMT and E-ELT are of comparable quality.
