  The anisotropy of the positrons emitted in the reaction $\bar{\nu}_{e}+p\to
n+e^{+}$ has to be taken into account for extracting an antineutrino signal in
Superkamiokande. For the Sun, this effect allows a sensitivity to
$\nu_{e}\to\bar{\nu}_{e}$ transition probability at the 3% level already with
the statistics collected in the first hundred days. For a supernova in the
Galaxy, the effect is crucial for extracting the correct ratio of $\nu-e$ to
$\bar\nu_{e}-p$ events.
