A deep imaging survey covering the entire 23 \arcmin diameter of the old open cluster M67 to V = 25 has been carried out using the mosaic imager ( UHCam ) on the Canada-France-Hawaii Telescope .
The cluster color-magnitude diagram ( CMD ) can be traced from stars on its giant branch at M _ { V } = +1 down through main sequence stars at least as faint as M _ { V } = 13.5 .
Stars this low in luminosity have masses below 0.15 M _ { \odot } .
A modest white dwarf ( WD ) cooling sequence is also observed commencing slightly fainter than M _ { V } = 10 and , after correction for background galaxy and stellar field contamination , terminating near M _ { V } = 14.6 .
The observed WDs follow quite closely a theoretical cooling sequence for 0.7 M _ { \odot } pure carbon core WDs with hydrogen-rich atmospheres ( DA WDs ) .
The cooling time to an M _ { V } of 14.6 for such WDs is 4.3 Gyr which we take as the WD cooling age of the cluster .
A fit of a set of isochrones to the cluster CMD indicates a turnoff age of 4.0 Gyr .
The excellent agreement between these results suggests that ages derived from white dwarf cooling should be considered as reliable as those from other dating techniques .
The WDs currently contribute about 9 % of the total cluster mass but the number seen appears to be somewhat low when compared with the number of giants observed in the cluster .