EVAPORATED ALUMINUM FILMS FOR ASTRONOMICAL MIRRORS

1. The aluminized mirror, if kept dry, will not tarnish. 2. Aluminum is the better reflector for the ultra-violet light. 3. The reflectivity of aluminum, for visible light, is almost as high as that of silver. 4. The aluminum surface may be cleaned of dust, oil, finger marks, etc., by washing with soap and water. The film adheres to the glass with such tenacity that it cannot be removed when Scotch tape is stripped from it. In fact, it has been found possible to rule a grating on the aluminum film. 5. Aluminum films do not scatter light. These properties make aluminum mirrors of particular value when used in scientific instruments.