Image of the [O III] emitting nebula (known as SDSO) and its surrounding area, including the Andromeda galaxy (top right). The [O III] flux is shown in cyan, while Hα+[N II] is shown in red. The green squares (surrounded by green circles) mark the location of the MEGARA pointings in and around the nebula presented in this work. The dashed square shows the area covered by our full-depth observations with the JAST80 telescope targeting [O II] and Hα with narrowbands J0378 and J0660, respectively. The RGB image¹ of the nebula and M31 was presented in Drechsler et al. (2023), and was obtained by Marcel Dreschler, Xavier Strottner, and Yann Sainty.