Plasmat lens further refines these achromats into triplets with the following design parameters: a high-index, doubly convex (DCX) lens cemented to a medium-index, doubly concave (DCV) lens cemented to a low-index meniscus lens. Up to this point, all refinements have maintained symmetry about the stop. The Plasmat further refines the Dagor form by uncementing the meniscus, allowing for placement away from the first two elements and removing the criterion of symmetry. In its most basic form, it is symmetrical and consists of two cemented groups of three lenses each. The innermost element in each group is a positive meniscus, the outermost is
Crepuscular rays Crepuscular rays Crepuscular rays (more commonly known as sunbeams, sun rays, splintered light, or god rays), in atmospheric optics, are rays of sunlight that appear to radiate from the point in the sky where the Sun is located. Shining through openings in clouds (particularly stratocumulus) or between other objects, these columns of sunlit particulates are separated by darker cloud-shadowed volumes. Despite seeming to converge toward the light source, the rays are in fact near-parallel shafts of sunlight. Their apparent convergence is a perspective effect. This phenomenon mimics the way parallel railway lines or long hallways, for example, seem to seek