another cheaper technique, lucky imaging, has had good results on smaller telescopes. this idea dates back to pre-war naked-eye observations of moments of good seeing, which were followed by observations of the planets on cine film after world war ii. the technique relies on the fact that every so often the effects of the atmosphere will be negligible, and hence by recording large numbers of images in real-time, a 'lucky' excellent image can be picked out. this happens more often when the number of r0-size patches over the telescope pupil is not too large, and the technique consequently breaks down for very large telescopes. it can nonetheless outperform adaptive optics in some cases and is accessible to amateurs. it does require very much longer observation times than adaptive optics for imaging faint targets, and is limited in its maximum resolution.