title: General analysis of aplanatic cassegrain, gregorian, and schwarzschild telescopes.
abstract: The properties of two-conic reflecting aplanats are analyzed and discussed on the basis of third order aberration theory. Techniques for designing infinite conjugate two mirror aplanats and computing their image properties are developed. The secondary mirror alignment characteristics of Ritchey-Chrétien and aplanatic Gregorian telescopes are examined and neutral point locations defined. Design configurations corrected for a third Seidel aberration (astigmatism, image curvature, or distortion) are identified and their properties discussed. The properties of Ritchey-Chrétien and aplanatic Gregorian telescopes are compared.
authors.forename: W B
authors.initials: WB
authors.lastname: Wetherell
authors.forename: M P
authors.initials: MP
authors.lastname: Rimmer