Cropped image in the Ca ii 8542 Å line at an offset of − 275 mÅ with overlain PMJ detection areas (solid-blue) and corresponding computed best-fit ellipses (dashed-green) at time 23 min 27 s. Also indicated for reference are three pixel positions inside one of the detection areas, one closer to the sunspot centre (turquoise cross), the PMJ centre-of-mass-pixel (red ×-mark), and one closer to the edge of the penumbra (blue star). Detailed line profiles for these pixels are shown in Fig. 13.