negative meniscus lens

A negative meniscus lens has a steeper concave surface and is thinner at the centre than at the periphery.

A meniscus corrector is a negative meniscus lens that is used to correct spherical aberration in image-forming optical systems such as catadioptric telescopes.

Dmitri Maksutov may have been working with the idea of pairing a spherical primary mirror in conjunction with a negative meniscus lens as far back as 1936.

The Gauss lens consists of two lenses; in its most basic form, a positive meniscus lens on the object side and a negative meniscus lens on the image side.

In optics, a Mangin mirror is a negative meniscus lens with the reflective surface on the rear side of the glass forming a curved mirror that reflects light without spherical aberration.

However, where the Schmidt uses an aspheric corrector at the entrance pupil, Maksutov's telescope uses a deeply curved full diameter negative meniscus lens (a "meniscus corrector shell").

The Maksutov is a catadioptric telescope design that combines a spherical mirror with a weakly negative meniscus lens in a design that takes advantage of all the surfaces being nearly "spherically symmetrical".