Doppler tomography and trail spectra of the H|$\alpha$|⁠, H|$\beta$|⁠, and H|$\gamma$| emission lines during decline nights. Left: trailed spectrum of the emission lines; Middle: the reconstructed trailed spectrum; and Right: the Doppler tomography for each spectral line. The relative flux is depicted in a scale of colours, where black represents the highest intensity, followed by red, then blue, and finally yellow.