Spectral index curvature map of Abell 2256, calculated as ${\alpha }_{23\mathrm{MHz}}^{46\mathrm{MHz}}-{\alpha }_{46\mathrm{MHz}}^{144\mathrm{MHz}}$, where both spectral index maps are made with a common resolution of 39″ × 24″. Blue regions indicate spectral steepening towards higher frequencies and red regions indicate flattening at higher frequencies. The background contours show the 144 MHz intensity smoothed to the same resolution.