With this adapter you can use the front mounted etalon of the Lunt 35mm H-alpha telescope as a rear mounted etalon.
Be careful: you absolutely need the right D-Erf (mounted on the front of your telescope) and a telecentric beam.
Thanks to the T2 thread on the front and the back of the adapter you can also doublestack your Lunt LS35T etalon with another rear mounted etalon.
NOTE: Lunt 40mm modules will NOT fit.