Anisoplanatism occurs when light from different parts of a target object passes through different turbulent paths or optical imperfections. This lack of spatial invariance means a correction applied for one line of sight will fail for an adjacent one. It dictates the maximum field of view over which adaptive optics or corrective lenses remain effective.
Heard on the job
The guide star is too far off axis, so anisoplanatism is ruining our wavefront correction on the primary target.
Insider tip
The angle over which the wavefront error remains correlated is called the isoplanatic angle.