  AstraLux is the Lucky Imaging camera for the Calar Alto 2.2-m telescope and
the 3.5-m NTT at La Silla. It allows nearly diffraction limited imaging in the
SDSS i' and z' bands of objects as faint as i'=15.5mag with minimum technical
effort.
  One of the ongoing AstraLux observing programs is a binarity survey among
late-type stars with spectral types K7 to M8, covering more than 1000 targets
on the northern and southern hemisphere. The survey is designed to refine
binarity statistics and especially the dependency of binarity fraction on
spectral type. The choice of the SDSS i' and z' filters allows to obtain
spectral type and mass estimates for resolved binaries.
  With an observing efficiency of typically 6 targets per hour we expect to
complete the survey in mid-2009. Selected targets will be followed up
astrometrically and photometrically, contributing to the calibration of the
mass-luminosity relation at the red end of the main sequence and at visible
wavelengths.
