The B 2 Σ + →X 2 Σ + (0–1, 2, 3, 4 progression) electronic transition of 12 C 17 O + was first observed and analyzed by Szajna and Ke¸pa [Spectrochim. Acta A 65 (2006) 1014–1020]. We have now extended our previous studies. The use of high resolution conventional spectroscopic techniques has allowed first rotational analysis of the 1–2, 1–3, 1–4 and 1–5 bands of the first negative system in the 37,000–43,000cm −1 spectral region. Approximately 500 transition wavenumbers were measured with an estimated accuracy of 0.005cm −1 . The present data were combined with the previous measurements to yield an improved set of molecular constants for the B 2 Σ + (v′=0, 1) and X 2 Σ + (v″=1, 2, 3, 4, 5). The v′=1 and v″=5 vibrational levels were observed for the first time and the main molecular constants are (in cm −1 , one standard deviation in parentheses)B 2 Σ + X 2 Σ + B 1 =1.710792(20)B 5 =1.825694(23)D 1 =7.799(15)×10 −6 D 5 =6.085(21)×10 −6 γ 1 =1.9491(37)×10 −2 γ 5 =[8.381]×10 −3 The principal equilibrium molecular constants for the B 2 Σ + and X 2 Σ + states have also been derived and the vibrational terms values for the ground and excited states have been calculated.