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.

NOTE: This is the short version of the housing purpose for a Lunt with the Energy Reflection Filter removed. A complete module will not fit it.