We have used deep high-resolution Hubble Space Telescope ACS observations to image the cluster NGC 1978 in the Large Magellanic Cloud .
This high-quality photometric data set allowed us to confirm the high ellipticity ( \epsilon \sim 0.30 \pm 0.02 ) of this stellar system .
The derived Color Magnitude Diagram allowed a detailed study of the main evolutionary sequences : in particular we have detected the so called Bump along the Red Giant Branch ( at V _ { 555 } =19.10 \pm 0.10 ) .
This is the first detection of this feature in an intermediate-age cluster . Moreover the morphology of the evolutionary sequence and their population ratios have been compared with the expectations of different theoretical models ( namely BaSTI , PEL and Padua ) in order to quantify the effect of convective overshooting .
The best agreement ( both in terms of morphology and star counts ) has been found the PEL ( Pisa Evolutionary Library ) isochrone with Z=0.008 ( consistenly with the most recent determination of the cluster metallicity , [ M/H ] =-0.37 dex ) and a mild overshooting efficiency ( \Lambda _ { os } =0.1 ) .
By adopting this theoretical set an age of \tau =1.9 \pm 0.1 Gyr has been obtained .