Performance analysis for T.H.E.M.I.S image stabilizeroptical system. I. ()Télescope Héliographique pour l'Etude du Magnétisme et des Instabilités de l'atmosphère Solaire

This paper describes the performance of the optical image stabilizer system developed for the franco-Italian T.H.E.M.I.S. telescope, which is currently being built on the Canary Island Tenerife. T.H.E.M.I.S will be one of the largest solar telescopes, and will be the first to be manufactured with a real time tip-tilt correction system integrated into its optical train. A new method is described here for measuring image motions. This method is called granulation tracking. It is based on Fourier transform analysis. A servo-loop model is also proposed, based on experimental measurements and the known time properties of atmospheric turbulence, to deduce the image quality obtained after correction. Method sensitivity and accuracy under various terrestrial turbulence conditions are discussed.