Monocentric lens

Patent Pending A Monocentric is an achromatic triplet lens with two pieces of crown glass cemented on both sides of a flint glass element. The elements are thick, strongly curved, and their surfaces have a common center giving it the name "monocentric". It was invented by Adolf Steinheil around 1883.[11] This design, like the solid eyepiece designs of Robert Tolles, Charles S. Hastings, and E. Wilfred Taylor,[12] is free from ghost reflections and gives a bright contrasty image, a desirable feature when it was invented (before anti-reflective coatings).[13] It has a narrow field of view of around 25°[14] and is a favorite amongst planetary observers.