Key points are not available for this paper at this time.
Context. Airglow emission lines, which dominate the optical-to-near-infrared sky radiation, show strong, line-dependent variability on time scales from minutes to decades. Therefore, the subtraction of the sky background in the affected wavelength regime becomes a problem if plain-sky spectra have to be taken at a different time from the astronomical data.
Noll et al. (Mon,) studied this question.