Coma (optics)

In optics, "coma" refers to a type of optical aberration that occurs when light from a point source does not converge to a single point after passing through a lens or reflecting off a mirror. This leads to a blurring of images, particularly noticeable when viewing off-axis objects. Coma is characterized by distorted images that appear to have a tail or a comet-like shape, hence the name "coma.