  The correlation function of two identical pions interacting via Coulomb
potential is computed for a general case of anisotropic particle's source of
finite life time. The effect of halo is taken into account as an additional
particle's source of large spatial extension. Due to the Coulomb interaction,
the effect of halo is not limited to very small relative momenta but it
influences the correlation function in a relatively large domain. The
relativistic effects are discussed in detail and it is argued that the
calculations have to be performed in the center-of-mass frame of particle's
pair where the (nonrelativistic) wave function of particle's relative motion is
meaningful. The Bowler-Sinyukov procedure to remove the Coulomb interaction is
tested and it is shown to significantly underestimate the source's life time.
