Example of interpolation of α(θ) for TBS based on H.E.S.S.  data on Vela X  (Abramowski et al. 2012). The α nodes calculated according to Eq. (6) are shown as black circles together with the corresponding 1σ envelope (grey-shaded area). The dashed black line illustrates the interpolation line along which a β_i value will be obtained. The parameter Δθ is the bin width in θ. The shifted nodes α_shift are drawn as red diamond markers. See text for further information.