What extent are visual double stars really binaries to?

On the basis of CCD frames, collected from 2013 till now and obtained with the telescopes of ASV and NAOR, of visual double stars for which there exist orbital or linear elements, we have identified both components in the Gaia DR2 Catalogue. Since that catalogue contains precisely determined parallaxes for both components, we have compared them in order to establish exactly how close to each other they really are in space. Thus, the question of which double stars are really binaries, i.e. gravitationally bound pairs, can be answered more reliably.