Slit coverage over the slit-jaw image in Si IV 1400 Å (left) and Mg II (right). The pixel colours on the right represent the rejected (light blue) and retained (orange) spectra for a threshold in reconstruction error, and black any spectra that were removed during the preprocessing. To filter all observations from QS type spectra, we compared the retained areas in different observations. We have chosen the reconstruction threshold of 0.15, depicted here.