Just the one 2X APO barlow Davo. I thought about stacking 2 of 'em but I fiqure the more glass elements in the train the worse off I'll be, so I doubled the length of the xtension tube after the barlow instead.....Using the concept of the further away the toucam is from the barlow, the bigger the image scale.
Time will tell weather I've gone too far with it....In which case I own a hack-saw!...just chop a bit off!