[casstony]

Thought I'd post this info as it might be of use to others:
the sct adapter on my 2" GSO dielectric diagonal shares the same thread as the barrel on my GSO 2" eyepieces (the 26mm packaged with the Bintel dob and a 2" GSO superview). You can swap the sct adapter for the eyepiece barrel to convert the sct diagonal to a refractor diagonal.

I only realised this after purchasing a spare refractor barrel from Agena, which turned out to be simply a 2" eyepiece barrel.