1 Introduction

This is a new paper in a series of publications on astrometric investigations of double stars. A total of 312 micrometer measurements of 155 binary stars are reported here. The observations were made during three astronomical runs. In September 1998 and September 1999 they were carried out using the 152 cm Spanish telescope at E.O.C.A., Calar Alto observatory (Almería, Spain). In July 1999 the 50 cm refractor at the Côte D'Azur observatory (Nice, France) was used.

The procedure in all cases was the same as previously described for earlier runs performed with these instruments (Ling 1987; Couteau et al. 1989; Docobo et al. 1991; Docobo & Prieto 1993; Ling & Lanchares 1993; Ling & Prieto 1997).

Stars were chosen on the basis of the timeliness of a revision of their orbit, and/or for their astrophysical properties; in particular, some binaries with variable components were included.