New procedure for making schmidt corrector plates

We describe what we call the dioptric elasticity method of making Schmidt plates. An oversize disk is supported on a narrow metal ring. Within this ring, the air underneath is partially evacuated; a primary vacuum is formed under the outer annulus. The elastically deformed disk is worked flat. When the loads are removed, the disk takes on an excellent, smooth Kerber profile over the region interior to the supporting ring. This produces more highly aspherical surfaces (F/1) and is more convenient than the method attempted by Schmidt. We give the elasticity theory, discuss our shop methods, and show the very satisfactory results.