I know they are not really ideal, but really considering one. I've got a minor interest in astrophotography. Today was super clear with an excellent view of the sky, but it's -17 degrees with the wind chill. Looking up it got me to thinking about the mirror lenses. There are some Samyang 500mm with 2x converter and some other things for around $150 on ebay. Has anybody ever used these with the nex system? Was it worth the money? I have a friend that I'm getting a 200mm Rokkor from, need to meet with him to pick it up one of these days. Just not sure if 200 is long enough for really good shots.