  MAGIC is a system of two Imaging Atmospheric Cherenkov Telescopes located in
the Canary island of La Palma. Since autumn 2009 both telescopes have been
working together in stereoscopic mode, providing a significant improvement with
respect to the previous single-telescope observations. We use observations of
the Crab Nebula taken at low zenith angles to assess the performance of the
MAGIC stereo system. The trigger threshold of the MAGIC telescopes is 50-60
GeV. Advanced stereo analysis techniques allow MAGIC to achieve a sensitivity
as good as (0.76 +/- 0.03)% of the Crab Nebula flux in 50 h of observations
above 290 GeV. The angular resolution at those energies is better than ~0.07
degree. We also perform a detailed study of possible systematic effects which
may influence the analysis of the data taken with the MAGIC telescopes.
