whose nature could be connected with the cluster.
author:
- 'Simone R. Zaggia'
- Giampaolo Piotto
- Massimo Capaccioli
date: 'Received 29 May 1997 / Accepted 11 July 1997'
nocite:
- '[@Lee77]'
- '[@Shade88]'
- '[@Alcaino92]'
- '[@Trager95]'
- '[@Bailyn95]'
- '[@DJ93]'
- '[@Mand96]'
- '[@Ibata95]'
title: 'The Stellar Distribution of the Globular Cluster M55 [^1] '
---

10000

Introduction
============

The recent advances in our understanding of the structure and evolution of Galactic globular clusters (GCs) have been possible thanks to the advent of accurate CCD photometry. However, till few years ago, CCD photometry was limited to the internal parts of GCs due to the small fields of the detectors. All the information relative to the outer regions and to the tidal radius $r_t$, arise from visual (*by eye*) stellar counts made on Schmidt plates, especially by King and collaborators [@King68; @Trager95]. This methodology of investigation suffers from various problems and statistical biases; we list some of them:

-   The limiting magnitude of photographic plates, which is generally too bright to permit the investigation of the radial distribution of stars in an appropriate mass range;

-   the high uncertainty in the evaluation of background stellar contamination;

-   an insufficient 