venerdì, giugno 13, 2008

How different apertures behave under the same seeing

This movie shows a star's image as seen by different scopes under the same atmospheric seeing. The leftmost image is produced by a scope (roughly) the same size of the Fried's paramter, The second 1.5 times the diameter, the third 2.5 times, and the fourth 5 times. As seen the larger the diameter (comapared to Fried's scale) the more number of speckles appear in the image and the more damage the image has. Nevertheless, the overall image size shriks moving from left to right. We can think of this as the fact that, as the scope resolution imporves it becomes able to revela then atmospheric effects.
It is also interesting to note that, according to Fried's work, the smallest scope produces a image which is jerky, whereas the lergest, encompassing more atmosphere at any time, has less tilt and tip and more roughness.