3.1 A note on CCD numbering and nomenclature

In what follows, the naming of MegaCam CCDs follows the CEA-CFHT naming convention. The camera is composed of 36 CCDs numbered from CCD00 to CCD35 (?). CCD00 is at top-left (extreme North-East position) and numbers increase from left to right and top to bottom. When 1/2 missing CCDs are reported it means that one of the MegaCam output amplifiers did not work. In that case a 1/2-size CCD rectangle, as drawn in Fig. 2 has no data. These failures were very rare, limited to a 5 months long window in 2003, representing less than 0.3% of the data and are listed on the MegaPrime failures page8 .

These failures demand special handling in the pipeline, but they have almost no impact on the science. In this document a “MegaCam pointing”, or a “tile” denotes a 1 × 1 deg2 field corresponding to a target position of the Wide survey listed in Table30.