On-sky data obtained with the long-slit spectrograph in NIX. Left: image of a raw 2D L-band spectrum, with the various features labelled (the east side of the slit is indicated for an on-sky position angle of 0°). Right: extracted spectrum of the double star HD 36648 together with an atmospheric transmission profile taken from the Molecfit library. The rapidly varying transmission at <3.5 μm makes it hard to correct the spectrum in that region. At the long wavelength end, the cutoff is due to the L-broad filter. The blue spectrum in the cleaner part (with atmospheric features removed and slope normalised), shows the detection of Pf γ at 3.74 μm and Br α at 4.05 μm as expected given the A5 spectral type of this star.