Anisoplanatism

Anisoplanatism refers to the phenomenon where the Earth's atmosphere causes variation in image quality across different parts of the sky when viewed through a telescope or astronomical instrument. Because atmospheric turbulence isn't uniform, light coming from different stars or regions can be distorted differently. This results in images that are sharp in one area but blurrier in others, making precise observations more challenging. Essentially, anisoplanatism highlights the difficulty in correcting atmospheric distortion uniformly over wide fields of view, impacting the clarity and accuracy of astronomical imaging.