Comparison between a spectrum affected by instrumental flattening (red) and an unaffected spectrum (blue), both extracted from the same auroral region during PJ6. The affected spectrum, observed with the wide slit in a very bright area, exhibits a flattened shape with missing emission features particularly in the unabsorbed band. In contrast, the narrow-slit spectrum in the same region clearly shows the characteristic double-peaked H₂ continuum around 160 nm.