WAVE-FRONT RECONSTRUCTION FROM DEFOCUSED IMAGES AND THE TESTING OF GROUND-BASED OPTICAL TELESCOPES

A new method has been developed for testing the optical quality of ground-based telescopes. Aberrations are estimated from wideband long-exposure defocused stellar images recorded with current astronomical CCD cameras. An iterative algorithm is used that simulates closed-loop wave-front compensation in adaptive optics. Compared with the conventional Hartmann test, the new method is easier to implement, has similar accuracy, and provides a higher spatial resolution on the reconstructed wave front. It has been applied to several astronomical telescopes and has been found to be a powerful diagnostic tool for improving image quality.