| Description: | This mosaic image of the region of crater Theophilus was made on april 1 2009, with a 200 mm F/25 Schmidt-Cassegrain telescope using a DMK31 camera. Each image is the result of a stack of the best of 750 frames out of an AVI movie of 1000 frames. The worst 250 frames, those that were significantly influenced by air turbulence, were rejected. Registax 5 was used to stack and pre-process the images while further processing was done with Photoshop. Although the theoretical resolution of a 200 mm telescope is 0.6 arcseconds, this image shows details smaller than 0.3 arcseconds. This is only possible if the contrast between the detail and its background is large enough. You can compare this with the visibility of dark electricity cables at a large distance: only the contrast with the bright air makes it possible to distinguish them. Of course, good eyesight is essential. Using the lucky imaging technique together with good seeing conditions and good optics, the effects of turbulence can be reduced, leading to images that reach the theoretical limits of resolution. |
