Top: spatial distribution of our target candidates (small dots), galaxies without Hα detections (open circles), and Hα-detected galaxies (filled circles) for the two observed (proto-)clusters. The large dotted circle in both plots denotes the available KMOS patrol field with a diameter of 7.2 arcmin or ∼3.7 Mpc at the redshifts of the (proto-)clusters. Bottom: redshift distribution of all 36 Hα detections for both (proto-)clusters combined (large plot) and for the two (proto-)clusters individually (inset graphs). Only two field galaxies are found (shown as gray filled circles in the upper panel), demonstrating the efficiency of the target selection. Both (proto-)clusters reside at a redshift z = 1.47, which we aimed for by selecting overdensities of [O II] emitters at z ≈ 1.5 with combined broad- and narrowband data. Interestingly, the two (proto-)clusters show similar substructure in redshift space.