(4) |

Figure 5:
The points are
displayed in the complex plane (small open squares) for
the frequency corresponding
to the highest peak of (, in Fig. 1).
The black square (1) represents the center of gravity of
these points, while the open square (2) opposed to (1)
on the circle, is the best position for t_{N+1}
(modulo ) to reduce the amplitude of
G_{N} at |

We would like to thank S. Paltani, G. Burki, F. Kienzle, C. Fluetsch, D. Kurtz and the reviewer A. Milsztajn for their interesting discussions and comments. Furthermore, we thank very warmly D. Minniti for his helpful and efficient collaboration.

Copyright The European Southern Observatory (ESO)