  We report on the observation of a significant deficit of cosmic rays from the
direction of the Moon with the IceCube detector. The study of this "Moon
shadow" is used to characterize the angular resolution and absolute pointing
capabilities of the detector. The detection is based on data taken in two
periods before the completion of the detector: between April 2008 and May 2009,
when IceCube operated in a partial configuration with 40 detector strings
deployed in the South Pole ice, and between May 2009 and May 2010 when the
detector operated with 59 strings. Using two independent analysis methods, the
Moon shadow has been observed to high significance (> 6 sigma) in both detector
configurations. The observed location of the shadow center is within 0.2
degrees of its expected position when geomagnetic deflection effects are taken
into account. This measurement validates the directional reconstruction
capabilities of IceCube.
