CaT lines in 1/3D (non-)LTE. The line centre wavelengths are shown for the dominant isotope (solid grey) and other isotopes (dotted grey). Top panel: metal-poor dwarf with stellar parameters T_eff = 6500 K, log g = 4.0, and [Fe/H] = −3. Bottom panel: metal-poor subgiant with stellar parameters T_eff = 5500 K, log g = 3.0, and [Fe/H] = −3. All spectra is computed at an abundance corresponding to [Ca/Fe] = +0.4, microturbulence ξ_mic. = 1.5 kms⁻¹ (for the 1D synthesis) and no macroturbulent broadening.