Effect of the constraint on the residual derivatives (Eq. (20)) on the separation of the point source and pixel channel. A radial cut through a simulated image is shown. Left: the black line shows the data, which is the sum of a point source and an extended source (dashed line). The deconvolution is performed with no constraint on the derivative image, resulting in a “hole” in the profile of the deconvolved extended source, shown in blue. Middle: the deconvolution is now made including a penalization of the first derivatives in the residuals. Right: same as middle, but using the second derivatives. The pixel channel is now well compatible with the input of the simulation.