2 Observations

All our observations were obtained with a CCD camera attached to the 91 cm Dutch light collector at ESO La Silla (Chile). The data presented here concern double stars mostly, acquired during the campaigns of Aug. 13-17 1992 (PL), Nov. 10-15 1992 (EO), Dec. 23-28 1993 (PL), Aug. 17-21 1994 (PL) and Nov. 11-15 1994 (EO). In these runs we used the coated GEC CCD chips ESO #7, #29 and #33. The basic CCD characteristics are listed in Paper I. With the given focal distance of 12.51 m, theoretical scale values correspond to 0.363 arcsec pixel^-1 (chip #7) and 0.445 arcsecpixel^-1 (chips #29 and #33). In agreement with the network protocol (Paper I), we choose from the standard filter set a Bessel V (ESO #420) and a Gunn i (ESO #465) filter, supplemented by neutral density filters when needed. It was necessary to carefully monitor the focus throughout the night because of a systematic drift and a rapid focus degradation. This resulted in an acquisition rate much lower than expected. A precise determination of the difference in focus position between the filters V and i at the Dutch telescope (due to different thicknesses of the glasses) was thus obtained and applied once the focus was adjusted in any of the used filters. This allowed to observe with the highest possible angular resolution in each filter. In general the seeing in the filter i was slightly smaller than the one in the V filter. The total number of observations presented here consists of 253 observations of 239 Hipparcos programme stars, 14 observations of 12 "astrometric standards'', more than one hundred observations of some 80 different photometric standard stars over 15 nights (as well as  one observation of ADS 6223 and SAO 244567 each). In the mean, about 8 standard stars have been observed each night whenever it was possible, with extreme conditions varying between 5 and 11. Consult also Paper I for a general presentation of our programme.