Spectrum of argon in the range λ320–λ350: the spectrum in the middle panel was recorded with our moderate-resolution LoWEUS spectrograph at the EBIT-I electron beam ion trap at an electron beam energy of 1000 eV. Eye-guiding markers indicate visual line positions. Known Ar lines are labeled by the spectrum number, while contamination lines from oxygen are labeled by the element. Lines that appear in second order of diffraction are denoted by “2”. The approximate band pass function of the SDO/AIA λ335 channel is indicated in the top panel. The lowest panel of the figure shows a high-resolution spectrum at half the wavelength. Strong first-diffraction order lines in this spectrum may appear in second diffraction order in the spectrum in the middle panel.