Comparison of the original and filtered Hα images. Top image: Hα image after the standard data reduction process. Bottom image: Hα image we present in our work that iteratively modelled and subtracted (described in Sect. 3.2) the background of the original image. Both images are presented on the same scale. The original image is clearly dominated by over- and under-subtracted artefacts, while the new image has a smooth and uniform background, which retains the majority of the real Hα emission. Some diffuse Hα emission is lost in this process, however, the new image is a significant improvement that shows the underlying structure of the giant Hα filaments in the IGM.