Left panel: CMD of NGC 663. Black dots are the field stars from Pigulski et al. (2001). Red circles are cluster members with Hα photometry, blue circles are Be stars and magenta squares red giant stars that are confirmed cluster members (Mermilliod et al. 2008). Right panel: synthetic cluster of an age of log (t) = 7.3. Red points indicate stars with T_eff higher than 10 000 K. Blue circles represent stars with ω > 0.8 and magenta squares stars with log (T_eff) < 3.66. Isochrones at an age of log (t) = 7.3 are drawn (V_ini/V_crit = 0.40: solid lines, non-rotating: dashed lines).