This is the Henry Draper catalog (HD, Cannon & Pickering 1918-1924)
as distributed by the Astronomical Data Center in 1989 (Vizier
III/135A), with Gaia DR2 source_ids and positions added. The link to
modern Gaia DR2 was done through Fabricius et al's match between HD
and Tycho 2 (Vizier IV/25), TGAS to match Tycho 2 and Gaia DR1, and
Gaia DR2 to match against Gaia DR1.
