Differences in astrometric parameters as a function of the su of the differences between the Hipparcos and TGAS solutions for stars, as measured in a field of 18° radius centred on the Hyades cluster. The blue dots represent clean 5-parameter solutions in the Hipparcos data. The red dots represent primarily accelerated solutions (so-called 7 and 9 parameter solutions). The green dots were solved as double stars in the Hipparcos solution. The two black lines show the ± 3σsu levels. From top to bottom: parallaxes, proper motions in right ascension, proper motion in declination.