As Gary said the "T" ring will screw straight onto the back of the 1.25" adapter you've shown in your image. If your looking for something to connect to the camera to insert into the Star Diagonal then you need the end of one of these.
http://www.iceinspace.com.au/forum/a...achmentid=7408 The silver sleeve and ring that screw into the extender is removable and screws into the camera "T" ring. The camera can then be attached to the star diagonal. The biggest problem of doing it this way is an increase in vingetting.