coma, optical A defect of an objective mirror or lens in which rays of light, striking the objective away from the optical axis are not brought to focus in the same image plane. The result is that star images toward the edge of the field of view appear to have comet-like tails spreading radially out from the optical axis (negative coma) or in toward the axis (positive coma). Related entry aberration, optical Related category OPTICS AND OPTICAL PHENOMENA Also on this site: Encyclopedia of Alternative Energy & Sustainable Living Encyclopedia of History Transport Concepts & Designs (partner site) |