Fe II line at 2600.17 Å, showing a very deep cometary absorption between +25 and +40 km s⁻¹ in the December 6, 1997 observations. The average absorption depth is about 55 %, which is well above the size of the comet estimated using fainter lines from higher energy levels (~36 %). The deep absorption seen at −10 km s⁻¹ relative to the β Pic radial velocity is due to the interstellar medium, which is not seen in the other Fe II lines arising from excited levels.