Fig. 1

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Examples of observations analysed in this study from the Rome/PSPT (RP, columns 1–3) and SFO/CFDT2 (SF, column 4) telescopes. The images were taken on 31 March 2000 in the blue (1st column) and red (2nd column) continuum, and in the Ca II K line (3rd and 4th columns). The panels present raw (after the calibration of the CCD) intensity images (top row), limb-darkening-compensated contrast images (middle row), as well as horizontal (red) and vertical (black) profiles (bottom row) along the cross-sections of the contrast images shown in the middle row, as marked by the dashed green lines. The images have been rotated to display the solar north pole at the top. The raw images are shown to their entire range of values, while the contrast images are shown in the range [−0.05, 0.05] and [−0.5, 0.5] for the continuum and Ca II K images, respectively. In the contrast images, regions outside the ranges listed above are saturated and appear black or white.

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