Filters alone wouldnt have gotten you those shots anyway, even with the tracking mount. The 8" Dob isnt really made for long exposure astrophotography since the focal length is long and the mount doesnt track accurately enough for nebulas. You'd still need a field flattener, a guider, or a whole different setup like a small refractor on an EQ mount. Harmonics and gears matter way more than glass for this stuff. Maybe test each piece of gear by itself before stacking things together, that way you know what's actually slowing you down. The only filters that wouldve worked with your Dob are the cheap OIII or UHC ones for visual viewing, and those are like 60 bucks not 220.