An Extension of the Lens-Mirror System of Maksutov

Abstract

THE lens-mirror system described by D. D. Maksutov¹, in which the aberrations of a spherical mirror are corrected by a single sphericalsurfaced meniscus lens, while eminently suitable for telescope objectives of moderate relative aperture, combining the coma correction of the refractor with a virtual absence of secondary spectrum, suffers from two sets of limitations which restrict its possible application in other fields. In the first place, the higher order spherical aberration is too great to yield the highest resolving power at very great relative apertures (except at very small focal lengths). Secondly, since the system has only three variables apart from meniscus thickness, the oblique aberrations other than coma cannot be corrected simultaneously with spherical aberration and axial achromatism, thus restricting its use over large angular fields. The former limitation may be reduced by increased thickness of the meniscus, but this necessarily involves larger unconnected oblique aberrations.