Astrometry from mutual event and small-separation CCD imaging

In order to determine precisely positions of the Galilean satellites of Jupiter, it is useful that shortly before and/or after photometric observations of a mutual event, normal CCD imaging observation is also performed for the two small-separation satellites. Experimental observations showed that the two observational types, on the whole, could derive mean (O-C) s with very good internal and external agreement (about 15–20 mas).