Image frame obtained by Kanata/HOWPol. The four subframes consist of two pairs of ordinary and extraordinary images of a single field. The left and right pairs are denoted as pairs #1 and #2, respectively. The origin orientations of Wollaston prisms corresponding to the two pairs are offset by 45° (table 5). In each pair, the left subframe is regarded as an ordinary image. The FOV of a single subframe is ∼1″ × 15″, but the effective FOV for polarimetry is limited to ∼1″ × 8″. North is up, and east is left.