Use of the Hartman sensor to measure the unisoplanatic wavefront tilt

It is shown that the Hartman wavefront sensor can be used to measure the degree of unisoplanatism under atmospheric wavefront degradations. The measurements conform with theory and show the size of the isoplanatic patch in the object space and the coherent distance at the entrance of the pupil plane. These two measurements are unequal because of inhomogeneous turbulence. This inhomogeneity can be accounted for by using known theory and the height of the line of sight above the ground.