  Let $H$ be a Hopf algebra, and $A$ an $H$-Galois extension. We investigate
$H$-Morita autoequivalences of $A$, introduce the concept of $H$-Picard group,
and we establish an exact sequence linking the $H$-Picard group of $A$ and the
Picard group of $A^{{\rm co}H}$.
