Observations of visual double stars at Pulkovo continue stellar astronomy
studies, which were started by F. Struve in 19 century and have become traditional
for Pulkovo observatory.
The scientific purpose of Pulkovo program of complex study of
visual double stars is the determination of basic kinematic and dynamic
properties of double and multiple stars located in neighbourhood of the Sun.
The first goal of this program is to find close (up to 100 parsec) double stars,
which have significate proper motion.
The next goal is to obtain dense homogeneous series of relative positions
of double star components for the determination of their orbits and masses,
and for revelation of possible invisible satellites.
Till 1941 observations of double stars were performed, mostly, on the Normal Astrograph, and since 1960 and till present time they have been performed on 26-inch refractor of Pulkovo observatory. Till 1995 there were only photographical observations, and since autumn of 1995 - photographical and CCD observations.
The 3rd database contains relative positions of selected double and multiple stars, and stars with possible invisible satellites. The database requires catalog of relative positions of visual double stars, based on photographic observations performed since 1960 on Pulkovo 26-inch refractor, and similar catalog based on CCD observations, obtained since 1995. The database also requires results if long-term observation series of ADS7251 and 61 Cygni. Presented material makes it possible to determine orbits and masses of double stars, and to perform various studies in stellar astronomy.