Distribution of the 2 129 659 clusters of objects extracted from the Gaia DR2 catalogue. They are composed of three and four images that pass the soft astrometric test (see Sect. 2) that have a maximum angular separation between components that is smaller than 6″, that have absolute differences in G magnitudes of < 4 mag, and that are found in regions of the celestial sphere where the mean field density is lower than 6  ×  10⁴ objects deg⁻². Lower density regions near the galactic centre can be explained by the filtering occurring in the on-board processing in order to prevent memory from saturating in such very dense regions of the sky (Gaia Collaboration 2016).