By the introduction of a rotating mirror near the exit slit of a Rowland circle mounting, we have designed a rapid scanning spectrometer capable of being synchronized with a short duration source of radiation. The wavelength range 1150–2000 A˚ is covered in 345 A˚ increments by setting the entrance arm at each of several predetermined angles of incidence. Spectral measurements of the vacuum ultraviolet (vuv) carbon monoxide fourth positive system are presented. The spectra have been obtained at a scan speed of 300 A˚/msec, and the conversion from a time scale to a wavelength scale is shown to be linear.