I think I finaly found the best telecompressor for use with my set up. I have an SBIG ST-2000XCM, Meade 12 RCX (f/8). While the Meade 6.3 and 3.3 both seemed to work--getting focus was tough. The AP .67 shows no coma edge to edge and provides a full fram flat field for easy focus at f/5.34. With the bader planetarium adapters (from AP) the AP .67 screw right onto the nose piece for easy insertion into my VanSLyke focuser. SO far, I like it.