I have a trinocular boom-arm stereo "dissecting scope" from USA Scopes (SMT-3412 SM), and the working distance is terrible. I want to buy a barlow (reduction lens) to increase working distance. My understanding is that they are attached to the existing objective lens rather than replacing the objective lens. I wrote USA Scopes, and they said they have a 0.5x auxiliary lens, but the thread diameter is the same as the objective lens (where it screws into the scope) and not the same as the "distal" threads on the objective lens. Is my understanding of the Barlow lens correct? I.e. the Barlow should be attached to the objective rather than a replacement of the objective? @Ptychodus04?