Graphical description of the masking procedure for the OmegaCAM field. Left panel: star haloes and ghosts hand-drawn around bright stars in the r band. The magenta star is the central pixel of the OmegaCAM field, the blue stars are all the stars with Gala mag G < 13, the red circles are the hand-drawn halos centered around the corresponding star, and the orange circles are the hand-drawn ghosts placed in a radial direction concerning the field center. Hand-drawn haloes and ghosts are generated for a limited sample of the bright stars. Blue lines connect the center of the ghosts with the center of the field. Using the sample of hand-drawn haloes and ghosts (position, diameter, and magnitude of the star), we built amaskforallthe bright stars. Right panel: maskforallthe stars brighterthan Gala magG < 13. The procedure to generate the maskis calibrated from the regions visually identified in the left panel and applied to all the bright stars in the field. On both panels, north is up and east is left.