Internal precisions in right ascension and declination to all stars from the observations of the sky paths. These precisions were determined as follows: standard deviations were grouped in bins of 0.5 mag and then the mean value was taken. The standard deviations of each star are obtained from the global reduction technique (see Sect. 3) by considering each position of the star and the resulting mean position. Each symbol represents the average of at least 1000 measurements.