The VIRMOS deep imaging survey. II: CFH12K BVRI optical data for the 0226-04 deep field

In this paper we describe in detail the reduction, preparation and reliability of the photometric catalogues which comprise the CFH12K-VIRMOS deep field. This region, consisting of four contiguous pointings of the CFH12K wide-field mosaic camera, covers a total area of 1.2deg 2. The survey reaches a limiting magnitude of BAB ~26.5, VAB ~ 26.2, RAB ~ 25.9 and IAB ~ 25.0 (corresponding to the point at which our recovery rate for simulated point-like sources sources falls below 50%). In total the survey contains 90,729 extended sources in the magnitude range 18.0