thanks John, the Hotech looks good and has the thread for bigger t ring which should help with vignetting. i have found another flattener which is stated to work well with rc8 and 10 and if i couple this with a wide t ring hopefully wouldnt get any vignetting
http://www.teleskop-express.de/shop/...reduction.html
At least there are a few options out there for big sensors on these rc's