Correspondence with G.W. Bothwell and S.C.B. Gascoigne regarding the Cassegrain focal surface, corrector lenses, the Hewlett-Packard laser interferometer and the computer control system. There are copies of letters from G.W. Bothwell to W.A. Goodsell of 12 November 1970, enclosing a note by G. Ohlsen, GEC-Elliott Process Automation Ltd, entitled 'Anglo-Australian 150 inch Telescope. Computer Design Study: Preliminary Configuration', and of 26 November 1970, containing a budgetary estimate for the computer design study. There is also a letter from Gascoigne to Redman, 27 November 1970, enclosing a draft specification of the prime focus correctors for the 150-inch telescope, and Redman's reply of 4 December, containing comments by himself and C.G. Wynne on this subject.