THE new solar telescope of the University Observatory, Oxford, which was formally declared open by the Vice-Chancellor on June 11, is in its essence a vertical Cassegrain telescope of 12 J inches aperture and 73 feet focal length. It gives a solar image some eight inches in diameter, and unlike the original tower telescopes (the 60-ft. and the 150-ft. at Mount Wilson) the present instrument is wholly free from chromatic aberration. Further, since the image is formed on the optical axis, the telescope is free from the extra axial aberrations characteristic of horizontal solar reflecting telescopes. Light is fed into the vertical Cassegrain telescope by a 16-in. ccelostat, driven by a synchronous motor, and a secondary mirror of the same aperture. Both coalostat and secondary mirror are provided with electrical slow motions which are controlled by a portable keyboard near the focal plane of the instrument; the same keyboard also carries controls for focusing the Cassegrain mirror.