Most telescopes are designed to eliminate this aberration. The images seen produce a V-shaped appearance. It is generally associated with poorly made optics or collimation errors. The center of the field may be sharp and in focus but the edges are out of focus and vice versa. The proper alignment of the optical elements in a telescope.
Collimation is critical for achieving optimum results.
Poor collimation will result in optical aberrations and distorted images. All shipping and handling charges listed are for U.S. lower 48 states.