NGC 6086 error value associated with the spectral index map at different resolutions between 144 and 675 MHz. Left: NGC 6086 error value associated with the spectral index map at 30 arcsec. Contours show the LOFAR emission and are drawn at 3σ. Right: NGC 6086 error value associated with the spectral index map at 7 arcsec. The region is above 3σ for all the frequencies. The beam is shown in the bottom-left corner, and a reference physical scale is shown in the top-left corner.