Left: VESTIGE maps of the 104 deg² within the NGVS footprint with 1419 independent frames in both the Hα NB and the r-band filters. To optimise the flat-fielding using the Elixir-LSB pipeline, the observations are gathered within an observing block of seven concatenated and adjacent frames, as depicted by the red and blue footprints here taken as two examples. The total number of observing blocks requested to cover the whole cluster is 203. Those obtained after the 2017A observing campaign are marked in grey with brightness increasing with the number of completed exposures (0 = white, 12 = dark grey). The dark regions in the outskirts of the clusters are the pilot observations completed in 2015 and 2016. Right: each sky region is covered by 12 independent frames dithered by 20 arcmin in right ascension (RA) and 15 arcmin in declination (Dec). This large dithering secures the sampling of the gaps between the different CCDs of MegaCam with a minimum of six exposures.