Spectrum of carbon and oxygen in the range λ320–λ350: the spectrum in the middle panel was recorded using our moderate-resolution LoWEUS spectrograph at the EBIT-I electron beam ion trap at an electron beam energy of 700 eV. Identified spectral features are labeled by the corresponding spectrum. Several oxygen lines appear in second diffraction order (marked “2”). The lowest panel of the figure shows a high-resolution spectrum (from our HIGGS spectrograph) 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. The approximate band pass function of the SDO/AIA λ335 channel is indicated in the top panel.