Rescaling Flux

Since the observations were performed on various nights under differentphotometric conditions and at different airmasses, each 1h exposureimage, derived from the recombination of the basic set of frames,has been rescaled to the same zero point and airmass before coadding with the others to produce the final image.In order to estimate the flux scaling factor, the magnitudes of the 20brightest objects (Ks>14) have been compared between frames.The uncertainties in the derived scaling factors are less than 0.03 mag.Once rescaled, the 11 Ks frames and the 5 J frames have been respectivelycoadded by Jitter as described in §§3.3.