The Radial Structure of the Galactic Disc

Three colour photometry on CCD frames in the Special Area SpA23 provides a deep probe of the galactic disc in a low absorption window towards the anticenter. Magnitudes to better than 10% at V = 25 and B-V colour down to V = 23 have been obtained. These new data, used in combination with lower magnitude photographic data in a wider field, give a strong evidence that the galactic density scale length is rather short (2.5 kpc) and drops abruptly beyond 6 kpc.