Sky observations (black) with various sky background models over-plotted for Run A (top panel), Run B (middle panel) and Run C (bottom panel). The observations taken at different ρ, 13, 20, 45, 90, and 110°, have been offset in flux for clarity. The different models are the current sky background model with F = 1.0 (green), the model run with the most likely extinction curve (optimal model; orange), and the best fit individual model (blue).