The 1-v″ progression of the Ångström band system, so far unobserved in the rare 13C17O isotopologue, was obtained under high resolution as an emission spectrum using a high accuracy dispersive optical spectroscopy. In the studied region 22 700-24 500 cm-1, 146 spectral lines were observed, among which 118 were interpreted as belonging to the 1-0 and 1-1 bands of B-A system, and the next 28 were interpreted as extra lines belonging to the 1-1 band of B1Σ+-e 3Σ- intercombination system, also unobserved in the 13C17O molecule so far. All those lines were precisely measured with an estimated accuracy better than 0.0025 cm-1, and rotationally analyzed. As a result the following in the 13C 17O molecule were calculated for the first time: the merged rotational constants B1 = 1.790 227(23) cm-1, D 1 = 6.233(47) × 10-6 cm-1, and ΔG1/2 = 2010.9622 (69) cm-1 and the equilibrium constants, ωe = 2076.04(57) cm-1, ωexe = 32.54(28) cm-1, Be = 1.824 678(15) cm-1, αe = 2.2967(24) × 10 -2 cm-1, De = 5.226(25) × 10-6 cm-1, and βe = 6.71(48) × 10-7 cm-1 for the B1Σ+ Rydberg state, as well as the individual rotational constant B0 = 1.504 85(78) cm -1, and the equilibrium constants ωe = 1463.340(21) cm-1, Be = 1.499 02(12) cm-1, αe = 1.778 2(49) × 10-2 cm-1, De = 7.36(56) × 10-6 cm-1 for the A 1Π state, and σe = 21 854.015(51) cm -1, RKR turning points, Franck-Condon factors (FCF), relative intensities, and r centroids for the Ångström band system. With the help of the strong and vast A1Π (v = 0) ∼ e 3Σ- (v = 1) interaction, the experimental parameters of the e3Σ- (v = 1) perturbing state were established in the 13C17O molecule for the first time. © 2013 American Chemical Society.