268M + Antlia 3nm filters on Esprit 120 at f/7
O3 was - 12 x 300s and 32 x 400s
Ha was - 44 x 300s
(no SII yet)
The issue is in Ha only. O3 was in a B3 location at New Moon. Ha was at a B3 location at Full Moon (but with decent separation, see attached). Trần's got longer subs (so I'm guessing not a light polluted area!) and is also picking up more stars.
I've raised this over on another Discord channel too; they seem to also think it's just bad calibration on my end, unless the 268M is good enough to pick up hydrogen emissions no one has ever seen
But that said, I'm still not 100% sure, because I can definitely see some background nebulosity in Trần's image, it's just much much more faint than mine.
Some of this nebulosity even lines up with the areas I'm picking it up.