The Loss in Resolving Power Caused by Primary Astigmatism, Coma, and Spherical Aberration in Telescopic Systems*

Abstract

The loss in resolving power caused by mixtures of, and by pure primary astigmatism, coma, and spherical aberration has been studied for telescopic systems. Resolution measurements were made by use of Foucault [ “ Memoire sur la construction des telescopes en verre argente,” Annales de l’observatoire imperial de Paris5, 217 ( 1858)] test objects of various inherent brightness contrasts. Results of these measurements were analyzed in terms of the magnitude of the aberrations expressed in terms of the Rayleigh [ “ Investigations in optics, with special reference to the spectroscope,” Phil. Mag.8, 411 ( 1879)] limit appropriate to the best visual focus for the telescopic systems under consideration. For high contrast test objects the loss in resolution was found to be of the order of five percent per Rayleigh limit and different for each aberration. The loss per Rayleigh limit was found to be greatest for astigmatism and least for coma. On a percentage basis, the loss in resolution caused by a given aberration was found to be greater for test objects of low contrast than for those of high contrast.