Optical image from the Digitized Sky Survey (left) and mid-IR image from Wide-field Infrared Survey Explorer (WISE, right), featuring the H II region S 171 in relation to the cluster Berkeley 59, which is located in the central white box. The northern part of the nebula is called NGC 7822. The large circle has a radius of 1.6° and shows the approximate extent of the H II region. The green contours show the 4 mm (70 GHz) continuum map from Planck. The smaller circles in the optical image mark the positions of the hottest members of the extended Cep OB 4 association; light blue circles represent spectral types O9 and B0, and yellow circles types B1 and B2. North is up, and east to the left. The WISE image is a colour composition of red (22 µm), green (4.6 µm), and blue (3.4 µm). Figure 2 is a zoomed-in view of the area in the white box.