In the design and construction of a large aperture optical system problems were encountered in figuring the optical elements and in mounting them to achieve mechanical stability. The various optical tests which were used to help overcome these problems on a system comprising refracting, reflecting, and Mangin elements are described. Test plates, star tests, OTF, Twyman-Green, and holographic techniques were all used at some stage, and the application for which each was used and the reasons why it was considered the most suitable technique are discussed.