TIGRE/HEROS spectra from days +3 (optically thick phase), +15 (transition phase), +42 (early nebular phase), and +121 (late nebular phase) after discovery. Blue channel. The spectra are blaze-normalized and subsequently normalized to a polynomial instrumental response function. No absolute flux calibration has been applied. Flux is shown on a logarithmic scale to better display the several spectroscopic features. The most relevant lines are numbered in italics, and for their identifications see Table 2.