So, at the risk of looking like an idiot, any reason why this might happen?
I bought this back in 2012, prior to the annular eclipse. I used it for many solar outreach events over the years, and always had at least some prominences to show folks. Then I didn't use it for a while, then brought it out again for several events in 2017 and 2018. But now I couldn't find any prominences to tune. I just get an orange disc, although I can see some the "orange peel" effect on the surface.
Last year, someone pointed out that you could tune beyond the range it came with by moving the screw that rotates the tuning knob. But he didn't find any prominences, either. Since then, I've tried numerous times, rotating in each direction, repeatedly pulling out and reinstalling the screw to tune far in each direction, but have not had any luck in seeing any prominences. I mean, NONE! I am able to focus and tune and still see the "orange peel" granulation on the disc, but no prominences.
So the question is, is there any part of a Coronado Solar Max II that can fail over time in a way that would make tuning for prominences impossible, but still be able to tune for "surface" detail? Have I just been picking days when there weren't any prominences to see? Have my eyes loss sensitivity at the H-alpha wavelength as I have aged (now 55)? Any ideas?