Telluric features around the oxygen forbidden line at 6300.304 Å on the spectra of HD 220197. HD 220197 spectra are shown in black and the shifted telluric spectra in dashed pink. The blue filled regions represent the range of ±0.15Å around the [O I] line, and the pink filled regions are the regions contaminated by the telluric features. The upper three panels show examples of contamination on the [O I] line, while the lower three have no contamination.