Masks, data, and models used to determine the best model of the disc. a: best model of the disc. b: KLIP-reduced data. c: best model of the disc after KLIP/ADI reduction. d: data subtracted by the best model, after KLIP/ADI reduction. e: mask used to select the part of the disc where the intensity scaling is done. f: mask applied to the data for the intensity scaling of the disc model. g: mask used to select the part of the disc where the χ² minimization is done. h: mask applied to the data, subtracted by the best model, for χ² minimisation. Masks e and g are based on approximate ellipse parameters, close to the disc parameters.