That allows for a 20mm Nagler to be used. I have a ep projection tube and am thinking about getting the smaller end threaded to screw into the T ring on the camera. The larger end fits nicely in to the focusser on the scope. BTW, H-alpha viewing is not as easy as it sounds and definitely requires adaptation to the very bright solar disc image.
Prominences are easy, surface details are another matter.
The nice thing is that I can stay inside and view through the window. That allows for a 20mm Nagler to be used. The larger end fits nicely in to the focusser on the scope. Prominences are easy, surface details are another matter.