You can find some info on those lenses by googling for "russentonne".
They are very popular in Europe..
Also, here you can find something about ways to improve the performance:
http://www.strickling.net/russentonne.htm
http://www.harpoint-observatory.com/...ussentonne.pdf
(NB: This not always necessary.. however in some cases the improvement is dramatic).
I have MTO-1000A and MC Rubinar 10/1000 Macro.. quite happy with them - definitely good value for money (they are more expensive recently.. couple of yeas ago they were half price (in US$)).
My personal experience is that you have to allow for cooling .. 1 hour is OK. Of course, this is for photographing, where the problems are much more visible than if you are using it for visual.
Also, the way the lens is mounted is critical - do not squeeze the tube - the mirror sits in the tube with very little tolerance and it is easy to deform it (this was driving me crazy for some time long time ago, when I tried to mount it with bracket, tightly fastened around the tube. The image in eyepiece was horrible!
This is illustrated in the thread below..
http://www.iceinspace.com.au/forum/s...ad.php?t=35180
BTW, I am using a trick when focussing with both MTO and Rubinar (by means of live view, Bahtinov mask should behave the same):
Since the front corrector assembly is heavy, it tends to "fall down" towards primary.
So I always focus by turning the collar from right to left, which moves the front with secondary mirror away from primary, in "up" direction - this prevents the focus to change by itself because of the helical thread backlash, it is already in lowest position.