2D diffraction pattern of a perfectly straight edge for λ = 2.2 μm on the surface of the Earth (top) as a function of the coordinate (x,y) on the ground, and two light curves (bottom) scanned perpendicular to the fringe pattern with local limb slopes of 0° (blue line) and of about 10° (yellow line). The light curves display different fringe spacing depending on the angle of the scan. Note that the diffraction pattern scales with .