2 Observations

Observations were carried out from May 1994 to August 1997 at the Venezuelan National Observatory. Two telescopes were used: the 1-m coudé reflector, equipped with a CCD camera, and the 65-cm. Zeiss refractor with a filar micrometer. The CCD camera is based on a Thomson TH-7883 chip, which features $574 \times 384$ pixels 23 $\mu$m square, giving a scale factor of 0.23 arcsec/pixel at the coudé focus. However, when the seeing conditions were good, a 1.5$\times$Barlow lens was used sparingly. The technique adopted to take CCD frame has been described in a previous paper (Abad & Della Prugna 1994). In brief, multiple images of the visual binary are taken onto a single CCD frame, shifting the telescope in R.A. by a small amount between exposures. To determine the scale factor, double stars from the Second List of Wide Visual Binaries were observed (Brosche & Sinachopoulos 1989). These were also observed at the refractor, in order to ascertain the screw-value of the filar micrometer. Previous micrometric observations at this telescope were carried out by A. Valbousquet (Valbousquet 1980) and C. Prieto (Prieto 1997). In this work, micrometric observations were carried out by one of the authors (FDP).