Left panel: 610 MHz GMRT image of A478 with its 3σ contour level in white where σ = 90 μJy beam⁻¹. The beam is 30′′ × 30′′ for both GMRT and LOFAR, and is shown in the bottom left corner of the image. Right panel: spectral index map between the 610 MHz GMRT and 144 MHz LOFAR images of A478. Contour levels from the low-resolution LOFAR image of A478 in Fig. 3 are overlaid in grey and black. Pixels below 3σ are blanked. The error map is shown in Fig. A.2.