Left panel: I_E image of UGC 2665 galaxy “unwrapped” in polar coordinates in terms of radial distance from the centre of the galaxy (r) and azimuthal angle around the disc (θ). Right panel: Original image in greyscale. Logarithmic spiral arms have been drawn on the left-hand panel on the prominent dust lanes in cyan colour crosses. Spiral arms are shown projected back onto the galaxy disc on the right panel.