Have you taken frames without the reducer? And then remove filters from the light path. Just trying to eliminate possible reflection sources.
I was imaging for roughly 2 months without the .7 reducer and never noticed the triangle or the dimmer repeated halos.
Your collimation is very suspect. Also I think (hard to tell for sure) that your spacing may be a bit over what's needed for best corner stars.
And then there's the microlensing effect. And then there's some problem with filter (I checked out Lum, and the *second* brightest star has a halo that it shouldn't have).
But basically, it would take a very high quality setup indeed to image a star this bright properly, with a camera with perfect anti-reflection coatings, and expensive filters. Not at this price point.
IMO, if you fix your collimation, upgrade your filters (is this the *new* ZWO set, or an older one? Doesn't look much improved from my old one) and avoid super-bright stars, you'll get some very nice images.
My collimation was definitely off as I didn't have enough time to collimate when I took these test shots. This is definitely still a problem even when collimated correctly. My guiding was also off as I had removed an OAG that I would usually have in the optical path to test if my reflections were coming from the OAG (they weren't).
My spacing is exactly at 105 not accounting for filter (which would put it at 106ish). It's not perfect, but as close as I could get it for the purposes of running this test:
With Celestron 0.7x reducer: Recommended 105 mm
Celestron T-Adapter: 50mm
Adapter extension (comes with Celestron T-Adapter): 28.5mm
ZWO 8 Position Filter Wheel: 20mm
ZWO ASI1600MM-cooled: 6.5 mm
I'm aware of the mirco-lensing as that is an artifact from the ASI1600mm Pro. Not the prettiest stuff, but I can live with it.
I bought the filter set this year in February from OPT. Not sure what I got. Is there anyway to check?
I also double checked the Filter Sides as well as reversing the filters. I also tried the empty slot on the filter wheel to see what happens there.The triangle is still there as well as one of the reflection donuts.
My main concern at the moment is that it might be the .7 reducer as I've never had the triangle thing before this. The star in the image is VEGA which is usually one of my focusing and star alignment stars.