Red: Fresnel diffraction intensity from the 2D FFT computation Eq. (2). Black shows the Hankel computation Eq. (5) as a reference. The occulter is a sharp-edged disk of radius 710 mm set at z = 144.348 m. An array of 156 000 × 156 000 and a sampling σ = 22.6 μm have been used. Panel a: full range, in logarithmic scale. Panel b: zoom in the Arago bright spot in the central region [0, 500 μm], in linear scale. Panel c: transition region between shadow and light around 710 mm, in linear scale.