[Shiraz (Ray)]

is there any way to get a small positive lens inside the guide adapter to act as transfer lens. If you can do it, you could refocus the guider beam further out. I bluetacked in a positive correcting lens from an otherwise useless Barlow when I was messing around with an OAG, but I guess you could find something useful in any old eyepiece - you need a short focal length lens and will have to experiment with placement, but it does work.

the alternative would be to put a negative lens (essentially a Barlow) closer than the guider focal plane and throw the focal plane out further. The disadvantage of this is that the guide image will be larger and dimmer, which will make it more difficult to find a star - might be OK with binning though. Again, a suitable lens should be available in an old eyepiece or you could try an actual short 2x Barlow if you can get it down deep enough in the adapter

rough drawing attached