![cover image](https://wikiwandv2-19431.kxcdn.com/_next/image?url=https://upload.wikimedia.org/wikipedia/commons/thumb/8/87/Lens_coma.svg/640px-Lens_coma.svg.png&w=640&q=50)
Coma (optics)
Aberration inherent to certain optical designs or due to imperfection in the lens / From Wikipedia, the free encyclopedia
In optics (especially telescopes), the coma (/ˈkoʊmə/), or comatic aberration, in an optical system refers to aberration inherent to certain optical designs or due to imperfection in the lens or other components that results in off-axis point sources such as stars appearing distorted, appearing to have a tail (coma) like a comet. Specifically, coma is defined as a variation in magnification over the entrance pupil. In refractive or diffractive optical systems, especially those imaging a wide spectral range, coma can be a function of wavelength, in which case it is a form of chromatic aberration.
![Coma of a single lens. Each cone of light focuses on different planes along the optical axis.](http://upload.wikimedia.org/wikipedia/commons/thumb/8/87/Lens_coma.svg/300px-Lens_coma.svg.png)