With this adapter you can use the front mounted etalon of the Lunt 40mm 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 40mm etalon with another rear mounted etalon.
Solar images are provided by Richard Schrantz.
NOTE: Lunt LS40FHa Front Mount 40mm Double Stack Solar Filter will NOT fit.