Two examples of the quality of the model. The observed sky spectrum is shown in black with the full sky background model in red. The scattered moonlight portion of the model is given in blue. In both cases the model fits the observed spectrum fairly well. a) This observation was done with moderate amount of moonlight. The moonlight comprises roughly half of the overall sky background flux. b) This one was with a significant amount of moonlight, as can be seen by the increase in overall flux. The scattered moonlight completely dominates the amount of background light. See Sect. 3 for more details.