a, Profile along a central line in the trail of the occultation star (blended with Haumea) in a drifted image taken from Crni Vrh observatory before the main occultation. On the y axis we show the light intensity along the line. The line starts 40 pixels before the beginning of the trail and ends 40 pixels after the end of the trail to show the background level and that the transition from trail to background is not easy to identify. The horizontal line marks the mean intensity of the trail. The thick line represents a profile smoothed with a 10-pixel boxcar to filter the high-frequency noise. The x axis has been translated from pixels to time using the drift speed of 40 arcsec per minute, given the known pixel scale of the telescope. The vertical dashed-dotted lines at 0 s and 300 s mark the start and end of the integration, respectively. The ut at start of exposure was 02:59:19.50. The intensity is basically constant with time. Before 0 s and after 300 s, the line profiles decay to the background level of the image because the pixels there were outside the trail. Hence, before 0 s and after 300 s, the plot does not represent the intensity of the source but the intensity of the background. b, Same as a, but from the image at the time of the occultation. The ut at the start of the exposure was 03:04:50.11. The dashed vertical line at 185 s marks the approximate moment at which the occultation begins. The smoothed curve shows that a clear drop in the signal is produced and lasts until the end of the 300-s integration. ADU, analog-to-digital unit.