Position-velocity diagram (Dec, Vel) of OH absorption at 1667 MHz. This is a visualisation through the entire data cube as seen from the declination-velocity side. The 1665 MHz data overlap at velocities higher than about 160  km s^-1 (see Fig. 3 in Sandqvist 1973). The wedge scale indicates the OH absorption in Jy/beam. (“HNVG” stands for high negative-velocity gas.)