The central 4x4 arcminutes of a sum of B,V,I averaged frames in M67. The total exposure time is ~4 hours, the FWHM of point sources in the summed image is 0.85".
The nearby open cluster M67 is estimated to be 4 Gyr old based
on the luminosity of the main-sequence turnoff. In February 1997,
Chuck Claver (NOAO) Matt Wood (FIT) and I obtained very deep
images in B, V and I of two fields in M67 along with a
control ``off-cluster'' field in order to measure the luminosity
function of the white dwarf cooling sequence. If the termination of the
WD sequence occurs at a cooling age of 4 gyr, our confidence in
cluster ages based on main-sequence-turnoff luminosities will be
considerably bolstered.
The exposure times are: