A new focusing vacuum monochromator is described which incorporates features making available a simple and flexible double monochromator with a single control. The focusing is provided with a linear motion coupled to a nearly balanced linkage system which, coupled to the grating, satisfies the conditions of the Rowland mount. Entrance and exit slits, variable in width, are offset to either side of the plane of the Rowland circle, which is of one‐meter diameter. Transparent window valves allow isolating the lamp and detector chamber from the monochromator, maintaining vacuum while making visual or near uv checks through the instrument. A filter wheel is built in to obviate some of the difficulty with scattered radiation when the instrument is used singly. Two units have been built and mounted as to allow changeover to the double system. The latter has yet to be tried but, used individually, they make nice instruments.