I like my had since early June SM 90 III a lot with one etalon. Tuning is easy, prom performance is excellent and surface contrast good. Yesterday was able to use 280X that way. So far I don't care for it DSs. Prom performance is no where near as good, I can't use as much power, tuning much more complicated, there're more ghosts than a haunted house and I don't care for through the glass darkly look of the image. Surface features are easier to see but so far I've not seen anything with two etalons I couldn't see with one. I've used the DS unit at most 2% of the time. When activity picks up I may change my mind. Also given the complexity of having 3 tuners when DSs it's entirely possible I've not yet been able tune it optimally. David
Like you, I find the views with single stack more than good enough. I have owned two double stack scopes, but my main compliant is that they do dim the image considerably and this makes high power study difficult. I also use binoviewers and that further dims the image.
I had the Lunt DSII on my Lunt 8 and there iwhile it did slightly increase surface contrast, the reflections washed out prominence detail and the dimming make powers over about 80x just too dim for me.
Someone posted on how this could be reduced by removing a filter (which I am not so keen on doing) but the DSII also made the scope weigh far more and kind of overwhelmed my mount and that is a bad thing. My mount sits outside on the patio 24/7 in the elements. It is a light and cheap mount but it works well up to 120x with the Lunt 80 and with the DS, it was very shaky.
I know the surface contrast is a bit better with DS, but I just like the brigness, lightness, and simplicty of single stack. With the binoviewers, the surface detail is much improved over the single eyepiece view and I feel like it is stack and a half level detail vs my 60mm Double Stack.
I have learned that best for everyone else is not always best for me. SS is fine for me. I look at the sun almost every day and I see amazing things. I am content.
Edited by Eddgie, 07 January 2020 - 05:18 PM.