Ca II K and H lines as observed on December 23, 2015 using HERMES. Two Gaussians are fitted to the K non-photospheric feature with velocities of 4.3 km s⁻¹ (red continuous line) and 16.8 km s⁻¹ (blue continuous line). The strongest, stable 4.3 km s⁻¹ absorption is clearly detected in the H line, but the weakest, variable absorption at 16.8 km s⁻¹ is embedded in the noise of the H spectrum. Vertical red- and grey-dashed lines show the stellar and ISM radial velocities, respectively.