Differences in position and parallax between the primary data set (TGAS) and the Hipparcos catalogue for 86 928 sources: a) difference in right ascension, (αT−αH)cosδ; b) difference in declination, δT−δH; c) difference in parallax, ϖT−ϖH. Median differences at epoch J2015.0 are shown in cells of about 3.36 deg2. The position differences have not been corrected for the orientation difference between the Hipparcos reference frame and the reference frame of Gaia DR1. The maps use an Aitoff projection in equatorial (ICRS) coordinates, with origin α = δ = 0 at the centre and α increasing from right to left.
Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.
Data correspond to usage on the plateform after 2015. The current usage metrics is available 48-96 hours after online publication and is updated daily on week days.
Initial download of the metrics may take a while.