Abstract: A random wavelength access monochromator incorporates a pair of coaxial off-axis parabolic reflectors configured so that the spherical aberrations introduced by the reflectors cancel each other. Light enters through an entrance slit and impinges upon a first off-axis parabolic reflector that collimates the beam and directs it towards a stationary grating. The grating in turn defracts the light and directs it towards a high speed scanning mirror which reflects the defracted light onto a second off-axis parabolic reflector which in turn focuses the beam to an exit slit. Both off-axis parabolic surfaces share the same axis of revolution and the same collimated beam axis. In order to make the apparatus practical, the beam is folded twice so that the exit point is focused away from the internal path of the beam.