Hello all, I'm new here, I pretty much joined because of this product / thread!
I have tried a standard SkyWatcher 2x barlow screwed onto the front of my diagonals (just the lens group, not the whole thing). The barlow was giving way more multiplication of the focal length than I wanted and it needed a lot of T2 extension tubing so I don't recommend it! I then bought a T.S. Optics 1.6x glass path corrector / barlow and used that along with the short T.S. eyepiece clamp (the one mentioned a few posts above) to clamp the diagonal in place (although I possibly could have gotten away without it). While I would still prefer to reach focus at the scope's native focal length, this arrangement works fairly well and the field of view is only slightly more narrow than my 9x50 SkyWatcher Finderscope when using a 40mm Plossl eyepiece. Although I would say it's a more comfortable and better view than the 9x50 finder. It would be nice to get the barlow closer to the eyepiece, the thought of cutting the nose-piece on my diagonal shorter has crossed my mind.
The diagonals I used were the basic 1.25" SkyWatcher mirror diagonal that came with my Mak and the 45 degree erecting prism that came with my ST80. I am tempted to buy the Williams Optics 90 degree erecting prism, but then the light path would probably grow further still, leading to more barlow effect. If anyone knows of an even lower power barlow that can be screwed directly onto a diagonal I'd love to hear about it, or an eyepiece longer than 40mm focal length in a 1.25" format. There is a Baader 1.2x glass path corrector / barlow, but that is meant for a T2 thread.
I would have thought that the Baader T2 prism would have reached focus with the short T.S. eyepiece clamp, does this not work, or is the T.S. clamp on order and yet to be tested?
I think SkyWatcher have a very odd product here; it has ED glass which I doubt would make a big difference for guiding (probably better off using a 60mm non-ED design for the money I would have thought), but everyone seems to want to use it visually, but it's too long to focus with a diagonal! And for guiding it's odd because it uses a finderscope foot rather than a dovetail bar or clamp. I took the finderscope foot off the metal plate and drilled, tapped and mounted an ADM dovetail clamp onto the plate. Way better!