Analysis of the October 29, 2018 comet. Top: cometary absorption spectrum of October 29, 2018 observation in a⁴D Fe II lines around 2750 Å. The grey zone represents the radial velocity range [+60; +90] km s⁻¹, which was used to measure the cometary absorptions. Bottom: curve of growth of the same Fe II lines, showing the mean absorption depths measured in the [+60; +90] km s⁻¹ range (blue dots) and the two-parameter fitted model (red line) as a function of the line absorbing strength. The uncertainties on the absorption measurements are of the order of the marker’s size, thanks to the very good S/N (~100) of the October 29, 2018 observation.