Spectra of 2I around the 557.73 (left), 630.03 (centre), and 636.37 nm (right) forbidden oxygen lines at three different epochs (black line). Our best fit model, used to measure the G/R ratio, is represented in red. The black vertical mark indicates the position of the cometary line and the dashed mark indicates the position of the telluric line. (a) November 15, 2019. (b) January 29, February 1, and February 2, 2020. (c) February 22 and March 16, 2020.