Galaxy environment of GRB 120422A. The field size is 33′′ × 33′′. The left panel shows the Hα image (15 Å wide), which includes the emission line and the continuum. The middle panel shows the continuum centred at 8020 Å (6250 Å rest frame) to avoid the emission from Hα (obtained with a 513-Å wide filter). The right panel is the subtraction of the left and middle panel, which is a pure Hα image. The host, G1, and G2 are at the same redshift as the GRB (OT). Their projected distances are 7.3, 28.7, and 107.8 kpc from the GRB site, respectively (see Table 6 for details). The diagonal stripes are produced by the R = 8.24 mag foreground star that is 79′′ NW of the explosion site. To illustrate the power of this observing method, we highlight an object south of G1 that does not have an emission line falling in the observed bandpass.