Agfa motion picture topics (Apr 1937-June 1940)

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Grinding this Prism for the 200-Inch Telescope has taken this man four years — And he may finish in four more. ing, newsreel-fashion, at the time when that action was happening. This was greatly simplified hy the cooperation of my friend Marcus Brown, who is the optician in charge of making the telescope. His advice on the technicalities of telescope-making has been invaluable. He has shown me the things that ought to be filmed, and kept me constantly informed as to when they could be shot. In fact, he has become so interested in picturemaking that many times, when I could not be there to operate the camera, he has volunteered to take over the camerawork himself, and has acquitted himself most successfully. “Clean-U p” Spectacular Due to the lighting conditions, virtually all of the film has been photographed with wide-open lenses — largely with the / : 1 .5 fifteen millimeter wide-angle objective. The subject-matter is shown in some detail, showing how the grinding tools are prepared with two-inch squares of rouge accurately mounted in the metal tool and fastened in place with hot pitch. Some of these operations are illustrated with simpler scenes show Marcus Brown , Optician in charge of making 200-Inch Lens , with the Foucalt KnifeEdge used in testing the big lens. ing the same operations being performed on the many smaller lenses, mirrors and prisms being made lor the telescope, as well as the spectacular shots of the big lens. In this connection it is interesting to mention that during the four years this work has been going on, approximately 10,000 lbs, of rouge had been used on the big lens alone, and some S1/^ tons of glass have been ground away. It may also be worth mentioning, in view of the frequent newspaper reports that the construction of the mirror is “ahead of schedule,” that actually no schedule has ever been set: the work is simply proceeding methodically, and the job will be finished whenever the lens reaches its proper curvature and polish. Time is not a factor; perfection is. And there is no rule or precedent, for each batch of glass, each mould made from each batch, behaves differently in grinding, according to its individual structure. One of the most spectacular operations is cleaning up the big disc after each day’s work. After each session of grinding, the big lens must 15