Good one, Mick! How did you fix the focus? I have a Rockinon 500mm mirror lens but haven't dared use it on Astro yet. I think they are great lenses. Recently I took some photos of HMAS Canberra on exercise in the Bass Strait, and they came out pretty well considering the ships were far away. I also tried the 2X extender (ie 1000mm) and got a real "Spy "photo. I found the focus a bit hit and miss
