An analysis of the performance of simple refractive null compensators was done. Two types of correctors were studied--the Dall compensator and the Offner compensator. A framework was built for determining whether these simple null tests are adequate for a wide range of aspheric surfaces. Variables involved in determining a surface to be null tested are f-number, conic constant, and focal length. Examples are given on how to determine the best null test for several aspheric surfaces. Also of concern in the design of a null compensator was simplicity. Two elements were the maximum used for both compensators and all compensator surfaces were spherical
