In a new study on sulfur monoxide, new ab initio potential energy curves are developed for excited states A(3)Pi, B-3 Sigma(-), c3n, and C'(3)Pi and for three states that are unassigned in the literature, which we numerically name 3(3)Sigma(-), 4(3)Pi, and 5(3)Pi. All these excited states have allowed transitions from ground state, X-3 Sigma(-). The ab initio calculations were performed using the MRCI-F12+Q/aug-cc-pV(5+d)Z level of theory implemented in MOLPRO2015. On the basis of close-coupling R -matrix theory, fine structure absorption cross sections of isotopically substituted sulfur monoxide are calculated for wavelengths of 190-300 nm. The spectra are shown at the highest possible resolution (FWHH approximate to 0.15-0.18 cm(-1)) for reference and future studies. The effects of self-shielding and possible mutual shielding are discussed.