Upper panel: NGC 2419 colour magnitude diagram from data taken during commissioning nights 2016 Oct 19, 23, 24, and 26. The magnitudes are corrected for foreground extinction as indicated by the magnitude subscript. Shown are sources with S/N_J, Ks​ >  ​10 (blue circles), all detections (small grey dots), and the known RR Lyrae (and other) variable stars in NGC 2419 (large solid red dots). For reference, we show with a solid red curve an isochrone adopting the literature values for its age and metallicity and [α/Fe]​ = ​0.0 dex. Magenta and blue curves in the background show a comparison to enhanced [α/Fe]​ = ​0.2 and 0.4 dex isochrones (see Sect. 4.1). Middle and lower panels: number counts of stars as a function of magnitude and as a function of distance to the cluster centre. The green histogram shows the ARGOS number counts, while the red line shows the detected stars in non-GLAO data. (Details in Sect. 4.1)