Just to follow up. I did try my solar filter. It's a prototype 10A triple-cavity 90%-transmission H-alpha filter from Solar Spectrum and 1" in diameter. The best was at 1x with just the TNV objective. Looking out my window in skies that only show seven stars in Orion plus a vague blob near M42. More or less full-Moon skies. Plus hazy out.
Barnard's Loop was right there. I thought it was a cloud until I realized where I was looking. Flame and IC434 show up at 1x. M42 looks bloated. Because of the tilt, I cannot see all of Barnard's Loop at once. About half at a time. While the filter is very narrow, I am told that being triple cavity makes it a little less sensitive to tilt. The end effect is that there is a tilt effect but not as extreme as you might think.
I cannot believe I can see Barnard's Loop out my window in these skies. I waited too long to get the TNV.
I could not get Barnard's Loop at all in the 7nm Baader H-alpha. Not much of the Flame or IC434 at 1x either.
In the 92mm f/7 afocal with a 32mm Plossl, I can see the Flame and IC434. The Horsehead was indistinct with the haze. If I hadn't seen it on a clear night, I would not have noticed it. The 10A was only a little better than the 7nm Baader H-alpha in the scope (maybe because the 10A vignettes the 28mm field stop of the Plossl to 24mm). On M42, I actually liked the 7nm Baader better. I am guessing for afocal telescope viewing, a 2" 3nm filter is likely better. But for the 1x viewing, wow.
I noticed that my 8nm OIII and 13nm H-beta barely benefit from the TNV. Yes somewhat better, but not worth the hassle. The DPM NPB filter, with its H-alpha band pass, is a little better. So guess it is really about H-alpha and I guess IR, which I have not tried yet.
I expected full gain on the unit to be brighter even with almost no light coming in, but I guess it is good news that it doesn't flare out when there is no light coming in. It scintillates as I expected at full gain. And at the lowest gain, I would say it is about the same brightness as naked eye. In a really dark location (nighttime -> dark room -> dark closet with door closed), I find after accommodating the darkness, I can detect light naked eye almost as well as the unit at full gain, but the big difference is that in the unit I can make out shapes and naked eye it is just a sense of light.