Hello in U.S.A. ( or Europe,) The chance to see through a realy big telescope in the Netherlands is almost zero, Because there are not many of them. I own a 16 inch F6 ,and want to make a big one now, ( also the grinding part ). what can I expect from the difference between the sizes 20, 25 or 30 inch in performance, What are the prices for a 2 inch blank in those sizes.