This is the first time I double stack my SM40 with an internal module made from PST etalon, the contrast is superb! 0.1A difference is big enough to make a rather big difference!
To tune the etalons, I shall use the Tmax on the SM40 to adjust the internal reflection to just outside the field of view, and then I can turn the collar of the PST etalon module to get maximum contrast. Very nice indeed!
AR955 is around in the middle of the solar disc, no dark spot can be seen easily at low power (20mm with my Borg 45ED II), several very nice prominence can be seen too!
Then I remove the PST etalon, and everything back to normal, quite a lot of surface detail were gone, the image is far less contrasty... I shall say, the difference is rather huge!
It's time for me to go out now, and when I've time, I shall capture some shots with this new setup! However, to make it focus with my DMK, I shall need to place a small corrector in the nosepiece of the BF10 first.
The next step would be to use this internal module with a suitable ERF, on a bigger telescope!
Additional Remarks: The setup I used is different from PST+SM40 since we skipped the ERF of the PST, and thus the image is brighter. Notice that SM40 has built-in ERF so what I'm doing is just to sandwich the PST etalon between the SM40 and the BF10.
Also, double stacking two Solarmax filter will also mean two ERF in series. Thus, my double stacking configuration will result in a brighter image since only one ERF is used.