The f/10 is a slow focus. If you are shooting at prime focus, bracket your shots (no lunar filter). Start at 1/60th to 1/125 of a second. With lunar filter, 1/15 to 1/60. I have shot through LX200 at prime focus (I have a PK1000). You can use 100 ISO or 400. The Pentax will meter through the scope. Just add or subtract stops (exposure times) to make sure you get a decent exposure. Always bracket. Usually when I use eyepiece projection I add stops. With a 25mm I add 1 to 1 2/3 stops a 17mm 1 1/3 to 2 1/3 stops. Bracket them. You will get good results on most of them. Good Luck!!