rms residuals in separation from Titan according to NOE-6-2015-SAT ephemerides, with regard to the exposure time. The x-axis shows the mean rms residuals in separation and y-axis the difference in V-magnitude from Titan. Purple squares denote 30−35 s exposures, green circles 40−45 s exposures, and blue triangles 50−60 s exposures. Orange triangles denote previous measurements made by Pascu (1994).