Custom synthetic observation OBScustom (at 0.25 R₂₀₀ with Perseus density profile), based on the optimally custom-rescaled Braginskii-MHD simulation. From left to right: emission measure fluctuation δEM, spectroscopic temperature fluctuation δT_s and emission-weighted velocity v_ew maps. Top: line-of-sight integrated input fields from the rescaled MHD simulation. Bottom: output fields reconstructed from the synthetic observation OBScustom. The colourbars are set according to the input quantities. The values of the thermodynamic fluctuation fields are in percents of the average background quantities (see Eq. (E.3)).