As in the case of our FK6,
(using ground based data provided by the FK5 to improve Hipparcos' results),
we also used Boss' General Cat. (GC) to increase the number of stars
with such better data: The combination of HIPPARCOS and GC data gives
improved results for 20 069 stars.
This number of objects could be treated as single stars.
The catalogue gives proper motions
with a typical mean error of 0.66 mas/year (about a factor of
1.2 better than Hipparcos for this sample of stars).