Integrated M 54 spectrum y and the data fit y^pred (in red), both for SVD-MCMC (left) and Full MCMC (right). The data fit is related to the respective MCMC posterior mean f^mean through y^pred = Gf^mean. The plots in the second row show the relative residuals , where y is the measurement data. The corresponding band (in blue) shows the simultaneous posterior predictive 95%-credible intervals. Grey vertical bands show wavelength regions which have been masked to avoid sky-residuals.