Published online by Cambridge University Press: 12 April 2016
With the imminent completion of AGK3 in the northern hemisphere, and the prospect of results from the SRS programme in the southern hemisphere becoming available within the next few years, we may regard the problem of the establishment of a fundamental reference frame for proper motions down to about mpg = 11 as, in principle, solved. This reference frame, through the large number of stars involved, will be readily accessible to photographic observers, with carte-du-ciel type, and even longer focus telescopes, for the reduction of relative proper motions to an absolute system.