Abstract

The theory and practice of alignment of off-axis mirrors of conic section are discussed in terms of third order optics. The departure of a symmetric conic mirror from a sphere of the same vertex radius is derived. By a transformation of coordinates, this departure is applied to an off-axis section. It is shown that the off-axis section may be thought of as a surface containing astigmatism, coma, and spherical aberration when compared to a bestfit sphere. With this insight, we show how to determine the location of the optical axis when looking at the off-axis section from its center of curvature. Once this is known, the mirror may be placed in an autocollimation test and final alignment may be performed by observing the shape of the image.

© 1980 Optical Society of America