2 The CCD observation and measurement

All of the observations were obtained at the Sheshan station near Shanghai (E $121\hbox{$.\!\!^\circ$ }18417$, N $31\hbox{$.\!\!^\circ$ }09611$), where a 1.56 m reflector with a $1024\times1024$ pixels CCD chip is installed for astrometric purposes. The calculation and analysis made in our previous work show that the good performance of the telescope together with the better seeing at the station ensure us to obtain clear CCD images showing the major satellites on each good night. We were allocated 4-6 days of telescope time in each of the years 1995-1997. During the three-year observing run, 122 CCD images in all were obtained. A summary of the number of images of each satellite in each year is presented in Table 1. The specifications of the reflector and the CCD chip used were the same as in Paper I. We used an I-type filter with a central wavelength of 900 nm and full width at half maximum (FWHM) of 150 nm. All positional measuring of the satellites in each CCD frame was done manually with IRAF software.

 

 

Table 1: Number of images of each satellite.

Satellite	1995	1996	1997
Ariel	46	57	11
Umbriel	46	48	19
Titania	46	57	19
Oberon	46	57	19
Miranda	27	47	9
TOTAL	211	266	77