Les effets optiques de la turbulence atmosphérique dans les images astronomiques

. The often blurry appearance of astronomical images at a telescope focus is attributed to atmospheric agitation. The study of the light propagation through the turbulent Earth atmosphere has made it possible to understand the existence of optical turbulence resulting from di ff raction phenomena that accompany the refraction of light rays. Optical turbulence is described by parameters (Fried parameter, isoplanetism angle, coherence time, external scale) which characterize the amplitude and the phase of the wave front on the telescope pupil. We deduce the properties of the images (short or long exposure) formed at the telescope focus as well as the description of the e ff ects of turbulence on these images (scintillation, agitation, spreading) and on interferometric observations (piston e ff ect)