There has been only one European response to this post, so I thought I'd throw this in…
The binoviewer (only) is an astro-scope attachment, Chinese, and an optically inferior copy of the Denkmeier series (which cost 3 or 4 times as much as this thing did). I got mine from BCF (Telescope House, London) and it's superb astronomically, used with long focal-length eyepieces. The image light is split into two, so there's some loss of contrast and definition (plus light loss from multiple glass surfaces).
The major problem is its weight - a counterbalance is required at the other end of the SCT - the Denkmeier weighs twice as much. The eyepieces have to be focussed individually, making the marriage to a scope for birdwatching rather idiotic, as one could spend all afternoon tweaking and shifting the focus before concentrating on the birds. Match shooting folk don't have this problem, as their target won't move. Not, in my humble opinion, something which'll catch on over here, thank god.