%0 Journal Article %A Pérez Cagigal, Manuel %A Valle Herrero, Pedro José %A Colodro Conde, Carlos %A Villo Pérez, Isidro %A Pérez Garrido, Antonio %T Covariance of lucky images for increasing objects contrast: diffraction-limited images in ground-based telescopes %D 2016 %@ 0035-8711 %U http://hdl.handle.net/10317/6699 %X Images of stars adopt shapes far from the ideal Airy pattern due to atmospheric density fluctuations. Hence, diffraction limited images can only be achieved by telescopes without atmospheric influence, e.g. spatial telescopes, or by using techniques like Adaptive Optics or Lucky Imaging. In this paper, we propose a new computational technique based on the evaluation of the COvariancE of Lucky Images (COELI). This technique allows to discover companions to main stars by taking advantage of the atmospheric fluctuations. We describe the algorithm and we carry out a theoretical analysis of the improvement in contrast. We have used images taken with 2.2 m Calar Alto telescope as a testbed for the technique resulting that, under certain conditions, telescope diffraction limit is clearly reached . %K Arquitectura y Tecnología de Computadoras %K Atmospheric effects %K Techniques: high angular resolution %K Techniques: image processing %K 2209.90 Tratamiento Digital. Imágenes %~ GOEDOC, SUB GOETTINGEN