Panel (a) shows a close-up view of the slit 4 spectrum inside the boxed region in Figure 4(a). A random pattern can be noticed in the spectrum. The white patch in the lower half of the spectrum near x-axis pixels 40 and 60 is due to 5303 Å emission. The vertical black patch is due to the strong 5302.3 Å absorption line. Panel (b) shows the spectrum obtained after corrections for the random pattern. Panels (c) and (d) show the spectral profiles before and after correction, respectively.