Illustration of the source finding algorithm. First, the position from Epoch(N) is projected to Epoch(N+1) using the polynomial transformations. The transformed position is then used as an initial guess for the finder. Each grid square in the zoomed-in panel, which shows a NACO source profile, corresponds to a Gaussian search box of some side length. The fitter tries fitting a Gaussian profile to the pixels in each of the surrounding grid squares. The Gaussian fit with the lowest χ² (white circle) is then selected as the position for this star in the new epoch. For clarity, the search boxes appear here as a grid; however, the actual algorithm utilizes overlapping search boxes.