The white dwarf cooling age of the open cluster NGC 2420

We have used deep HST WFPC2 observations of two fields in NGC 2420 to produ ce a cluster color-magnitude diagram down to V approximate to 27. After imp osing morphological selection criteria we find eight candidate white dwarfs in NGC 2420. Our completeness estimates indicate that we have found the te rminus of the WD cooling sequence. We argue that the cluster distance modul us is likely to be close to 12.10 with E(B-V) = 0.04. With these parameters we find a white dwarf cooling age for NGC 2420 of 2.0 +/- 0.20 (1 sigma) G yr. The 0.20 Gyr uncertainty includes errors in the photometry, sequence fi tting, precursor timescales, and theoretical white dwarf cooling timescales . Comparing the cluster white dwarf cooling age to ages derived from stella r isochrone fitting we find a preference for ages derived from models incor porating convective overshoot.