Image-processing techniques in precisely measuring positions of Saturn and its satellites

After overcoming the deficiencies of previous image-processing techniques, a novel technique based on the edge-detection of Saturnian ring is developed to precisely measure Saturn's position. Furthermore, the scattering light (i.e. halo light) of Saturn and its ring is removed effectively based on its center symmetry. Therefore, we have much more opportunities to accurately measure the positions of Mimas and Enceladus-- two satellites very close to the Saturn. Experimental tests with 127 frames of CCD images obtained on the 1-meter telescope at the Yunnan Observatory over three nights show that the geometric center of the Saturnian ring and its 4 satellites (Tethys, Dione, Rhea and Titan) have the same positional precision, and the standard error for a single observation is less than ±0.05 arcsec. It is believed that these new techniques would have important impetus to the positional measurement of both Saturn by using a CCD meridian instrument and its faint satellites by using a long focal length telescope.