belong.

Despite the potential interest of this nearby cluster for problems such as the dynamical evolution of globular clusters and interaction with the tidal field of the Galaxy, the existing data on M55 are so far limited and have been used to address only particular problems. Now large field CCDs offer the possibility to attack this problems in a suitable way. The following Section is dedicated to the presentation of the M55 data set and our observing strategy; in Section 4 we show the luminosity and mass function of the cluster; in Section 5 we present the analysis of the radial density profile and the conclusions. The details of the techniques adopted in the reduction and analysis of the data can be found in the appendix of the paper.

The photometric data
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A whole quadrant of M55 was mapped (from the center out to $\sim1.5~r_t$, with $r_t=977''$ as in Trager, King, and Djorgovski, 1995), on the night of July 5 1992 with 18 EMMI-NTT fields ($7\farcm2\times7\farcm2$) in the $V$ and $I$ bands. Figure \[M55frames\] shows the field positions on the sky. For each field a $V$ and a $I$ band image were taken in succession, with exposure times of 