From top to bottom: Chip 2 extracted Bright_rim spectrum combined from 179 on–off spectra below 8600 Å (in blue) and 228 on–off spectra above 8600 Å (in red). A typical airglow spectrum scaled by 1/500 and shifted upwards by 20 cgs-units. The standard deviation of the intensities along the slit in the Chip 2 Bright_rim 2D spectrum shifted upwards by 4 cgs-units. The A_100″-off spectrum (green) from the sum of all 270 off–on–off spectra; it has been shifted upwards by 3 cgs-units. The A_100″-off spectra for the sub-sets of 179 and 228 individual spectra, selected for minimum-AGL residuals in blue and red for λ < 8600 Å and λ > 8600 Å, respectively.