The receiving scope is my 150 mm f/5 achromat equipped with a sturdy Tecnosky V-Power focuser that allows for 190mm backfocus, quite a lot for most purposes. I calculated that transplanting the Lunt into it required about 150 mm of focus travel so it seemed feasible without modifying the OTA, that is by simply inserting the Lunt module in the 2" eyepiece holder.
The PT red module of the Lunt can be easily separated from the white tube. These pieces are joined through a M68 standard thread, male on the module, female on the tube. I purchased from TS the following adapters:
- a Baader M68 extension tube 20mm long
- a M68 female/M48 male ring adapter
For inserting the Lunt module in the eyepiece holder of the OTA I made use of a M48 (2 inch diameter) extension usually sold as the 28 mm finetuning ring for Baader Hyperion eyepieces. All pieces were assembled this way:
Now one has only to put the Lunt module into the focuser
As my Lunt is already provided with a FT focuser I obtained a 2 focusers system. This is of course not necessary, those who have the basic version of the Lunt can leave in place that horrible helical focuser in the full retracted position or to unscrew it and replace with a T2 Quark adapter that has (telescope side) the same thread of the focuser, then put on the T2 male thread (BF side) a 1.25" eyepiece holder. This solution would be preferable as increases stability.
Before to point the OTA to the Sun I placed in front of the objective a 110mm Baader D-ERF. As its free aperture is of 104mm this provides a f/7.2 cone light.
Trying to use the system I immediately discovered that the original Lunt BF diagonal is unusable in this way, it is very dark and provides a strongly uneven field that can't be corrected through flats. In fact to image the whole disc of the Sun I have always been forced to put the disc on a side of the sensor area to reduce the unevenness. I am planning to replace the original BF with a Coronado one, in the meantime I made use of my Quark Chromosphere to which I removed the internal telecentric as I prefer to use an external amplifier. The overall system results to be quite long

but the first results, obtained in the very poor seeing of this very hot summer, are promising
There is still much room for improvements, of course, and I am now curious to try the Coronado BF, so this mod will probably keep me busy for several weeks

The mod is fully reversible and one can immediately reassemble the Lunt to its original state without effort. The cost of the mod, in this case, has been only that of the two above mentioned adapters.
Thanks for looking