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1 Introduction

After the publication of the HIPPARCOS catalogue, containing the results of this astrometric mission (ESA, 1997), one can but notice how scanty our data on visual binaries are, both from the photometric as from the astrometric point of view. Especially data on couples with separations in the order of a few arcseconds do not allow to evaluate their significance, or to make reliable statistics. It is therefore evident to us that ground-based observations of visual double stars with angular separations of a few arcseconds have to be continued; CCD's (not in use for very long yet, compared to the history of visual binary observing) provide new data of high reliability; statistical treatment of the new observations combined with the available old ones provides a strong tool for studying relative proper motions and thus to decide upon the nature of the objects (cf. Brosche & Sinachopoulos 1988 and Brosche et al. 1991).

The present results are a continuation of the observing programme we initiated more than ten years ago (Sinachopoulos 1988, Paper I). In the discussion we shall have particular interest as to what fraction of these relatively wide-separation stars show significant motion after (at least) several decades. Also compared to the previous articles in this series of papers, the objects chosen are closer to the possibilities the reduction technique affords, linked to the limiting seeing conditions; some additional comments concerning the reduction procedure are given in Sect. 3.1. Experience through all these years has shown that CCD detectors are very much suited for these observations, as e.g. Sinachopoulos et al. (1988) claimed.


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Up: CCD astrometry and instrumental stars

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