noun
Usage: usually capitalized S
: an optical system that utilizes an objective composed of a concave spherical mirror having in front of it a transparent correction plate carefully figured to offset the spherical aberration of the mirror
noun
Usage: usually capitalized S
: an optical system that utilizes an objective composed of a concave spherical mirror having in front of it a transparent correction plate carefully figured to offset the spherical aberration of the mirror
Webster's New International English Dictionary. Новый международный словарь английского языка Webster. 2012