[O III]/Hα ratios for the nova super-remnant, three supernova remnants, an H II region, and a planetary nebula. Top and middle rows: MCELS continuum-subtracted [O III] images of the six sources, each with a different field of view, as follows: ∼33′×33′ for the NSR; ∼3′×3′ for PN SMP LMC 80; ∼40′×40′ for H II region L77 DEM L45; ∼13′×13′ for SNR J0450-7050 (a.k.a. Veliki; Smeaton et al. 2025); ∼10′×10′ for SNR J0534-7033; and ∼20′×20′ for SNR J0506-6541. As detailed in Appendix A.3, slits with different lengths were placed across each structure (with different numbers of apertures) to derive ratios. These slits are shown in each panel. Bottom row: Comparison of the [O III]/Hα ratios for the six sources across the length of the slit with the x−axis normalised to the length of the slit. The nova super-remnant has two distinct groupings of ratios (between ∼0.05 − 0.13 and ∼0.86 − 0.95) corresponding to the northeast and southwest shell with low [O III]/Hα ratios. Two of the supernova remnants (J0534-7033 and J0506-6541) and the H II region have a high [O III]/Hα ratio across their full extent, while the SNR J0450-7050 has a high [O III]/Hα across the eastern edge. The [O III]/Hα ratios from the two apertures across the PN are also high, as expected. The transparent points are from apertures with flux sums ≤0.