  Using data collected by the MACRO experiment from 1989 to the end of its
operations in 2000, we have studied in the underground muon flux the shadowing
effects due to both the Moon and the Sun. We have observed the Moon shadowing
effect with a significance of 6.5 sigma and the Sun shadowing effect with a
significance of 4.3 sigma. The observed displacement of the Sun shadow, due to
the configurations of the solar and interplanetary magnetic fields, has been
used to quote the antiproton/proton flux limits for primaries of about 20 TeV
energy.
