2", F4 aplanatic coma corrector

Optimized for the super-fast Skywatcher F4 Newtonian telescope, this coma corrector ensures pinpoint stars right out to the edge of your exposure. It does not change the focal length. The back focus is 55mm.

A coma corrector is a corrective lens for Newtonian telescopes. This type of telescope can cause distortion of the image at the edge of the field of view, making stars look like little comets. This aberration is therefore called 'coma'.