Mirror-Making Machine, SIT Testing, and Shop Strategies

Jeff Baldwin is a mirror maker in Lathrop, just south of Stockton. He has made approximately 400 mirrors. Recently he and a friend made a mirror-making machine that will produce mirrors up to about 46" in diameter. He is also using the Slit Image Test (SIT) to produce high-precision mirrors of any diameter, any conic constant, and any focal ratio. The machine is programmable to do many styles of strokes and fixed-post grinding and polishing. In the future it will also have curve-generating abilities. This machine has helped Jeff work mirrors that are too heavy and large to physically manipulate.

The SIT was "invented" by Bill Thomas of Grass Valley, CA. It is a combination of Hartman, Caustic, and other tests. The test allows the user to have high-precision, works for large or small mirrors, fast or slow focal ratios, in stable rooms or in unstable rooms, and can be done very quickly. Its repeatability is outstanding. Even though it is a good idea to use other tests along with the SIT to finalize a mirror, the test enables the optician to process mirrors very quickly and accurately. The machine, the SIT, and shop systems all work together to make large aperture fast focal ratio parabolic telescope mirrors of high quality. Shop systems and strategies keep the optician working quickly, accurately, and safely.