  We discuss the CM diagram of the galactic cluster NGC2420 to the light of
current theoretical predictions. By relying on the most recent updating of the
physical input, one finds too luminous theoretical He burning stars together
with the evidence for a misfitting of the lower portion of the MS. Moreover one
finds two well known overshooting signatures, as given by i) the large
extension of the "hook" preceding the overall contraction gap, and ii) the
scarcity of stars just at the end of the gap. We show that the overluminosity
of He burning stars appears as a constant prediction of models based on updated
physics, whereas alternative assumptions about the Equation of State can
account for the MS fitting. Moreover, due to the scarse statistical
significance of the observational sample, one finds that overshooting
signatures can be present also in canonical (without overshooting) predictions.
We conclude that, unfortunately, NGC2420 does not keep the promise to be of
help in costraining the actual dimensions of convective cores in H burning MS
stars, suggesting in the meantime that using clumping He burning stars as
theoretical standard candle is at least a risky procedure. In this context the
need for firmer constraints about the reddening of galactic clusters is shortly
discussed.
