  As part of a stellar population sampling program, a series of photometric
probes at various field sizes and depths have been obtained in a low extinction
window in the galactic anticentre direction. Such data set strong constraints
on the radial structure of the disc. At the forefront of this "drilling"
program, very deep CCD frames probe the most external parts of the disc. Over
the whole effective magnitude range (18 to 25), all contributions in the
statistics which should be expected from old disc stars beyond 6 kpc vanish,
although such stars dominate by far at distances less than 5 kpc. This is the
signature of a sharp cut-off in the star density: the edge of the galactic disc
between 5.5 and 6 kpc. As a consequence, the galactic radius does not exceed 14
kpc (assuming $R/-/(//sun/)$=8.5). Colours of elliptical galaxies measured in
the field rule out the risk of being misled by undetected extinction.
