PERFORMANCE OF THE MACRO DETECTOR AT GRAN-SASSO - MOON SHADOW AND SEASONAL-VARIATIONS

The MACRO underground detector at Gran Sasso has recorded about 30 mil lion muon events in the period 1989-1995. We have analyzed these data to look for time variations and to study the pointing capabilities of the apparatus in the search for astrophysical point sources. We have o bserved a 3% seasonal variation of the high energy muon rate, due to a tmospheric temperature variations, in agreement with theoretical predi ctions. We report also the detection of the moon shadowing effect with a statistical significance of 3.7 sigma. The results obtained straigh ten the possibility that a ''muon astronomy'' using underground experi ments is possible.