Examples (from the stacked image) of variable candidates assigned to different quality classes, with the corresponding light curves. The white circles correspond to the 2″ diameter aperture and are centered on the object coordinates listed in the catalog. Objects labeled 1 (upper panel) are generally isolated and free from aesthetic defects. In the case of the objects belonging to class 2 (middle panel), potential problems (e.g., the presence of a neighbor) must be taken into account. Objects labeled 3 (lower panel) are probably spurious variable sources: an extended, elongated object with a very bright and close companion is shown as an example. The error bars correspond to our adopted threshold of +3×. The objects in the upper and middle panels are, respectively, Nos. 41 and 71 in Table 3 (see Sect. 5).