SED of PKS 2155–304 derived using csspec for the T200 dataset. Red data represent the unbinned ctools analysis, blue data are the values from Fig. 9 in Aharonian et al. (2009). The red line is the fitted curved power-law spectral model, the light red band is the 68% confidence level uncertainty band of the spectral model and was determined using ctbutterfly. 68% confidence level upper limits are displayed when the statistical error exceeds the value of a flux point.