PST etalon experiments

The sky is better today, so I did a series of experiments:

1. 2 red filters, Borg 45ED II, 2.5x corrector, PST etalon module, a lot of extension tube, BF10, UV-IR block

-> This is a successful test, prominences are shown nicely, but surface detail is minimal, I suppose this light cone is closed to f/10 and thus, the PST etalon is happier with it

2. 2 red filters, Borg 45ED II, PST etalon module, 2.5x corrector, BF10, UV-IR block

-> This one also works, but prominence is less contrasty

3. 1 red filter, Borg 45ED II, PST etalon module, 2.5x corrector, BF10, UV-IR block

-> Too much internal reflection, didn't work well


3. 1 red filter, Ranger, 2.5x corrector, PST etalon module, one extension tube, BF10, UV-IR block

-> This does not work, many internal reflections. The red filter used is lighter in color, and so the problem is worsen...

I suppose we need something like a T-max or simply more red filters to eliminate the internal reflections! At the same time, closer to f/10 definitely helps.

Strange is that, last time we did try f/8 and it works, too. Obviously f/10 is the best.

Also with two red filters, the sun at prime focus of my Borg is just slightly warm. But with one red filter, the sun at prime focus of my Ranger is very hot.