On the top-left is an image of saturn with aberrations from a 5” 30% obstructed SCT, on the top-right the same telescope but with 1/20 RMS roughness added. At first glance these image do look alike a lot. However after subtraction of the images the image on the right is showing that certain areas changed more than others. Small amounts of roughness are however not so problematic due to the smoothness of this aberration over a mirror-surface. |