Seven bands of theA2Δ–X2Π system of the13CH radical have been photographed in emission from a Geissler tube. Under high resolution and using Th lines as standards, as well as an interferometric comparator equipped with a photoelectric scanning device, the 0–0 band has been rephotographed, and the 1–1, 2–2, 3–3, 0–1, 1–2, and 2–3 bands have been photographed for the first time. The reduction of the spectrum for the individual bands has been performed via a nonlinear least-squares fit with the effective Hamiltonians of Brown. The merged molecular parameters for the observed levels and the equilibrium molecular constants were compared with calculations performed within the Born–Oppenheimer approximation and a small disagreement for some of them has been found, due to partial breakdown of the Born–Oppenheimer approximation. The electronic isotopic shift was determined for the first time: Δνe= 0.403 cm−1. The RKR potentials andr-centroids have been calculated for both combining states, as well as Franck–Condon factors for theA–Xsystem.