Ecliptic Aitoff projection with longitude zero at the centre and increasing to the left. Top: Sky density of the (unpublished) all-sky photometric sample, subsets of which for different period ranges are shown in Figs. C.2 and C.3. Bottom: Sky density of the (unpublished) all-sky astrometric sample, subsets of which for different period ranges are shown in Figs. C.6 and C.7. Both samples are introduced in Sect. 4.1. The green circle indicates the location of the GAPS catalogue (see Fig. 23).