I NEED HELP - SHO imaging

[marsh bronze]

I am quite new to narrowband imaging. I' having some problems with my SHO filters, which don't seem to let through any data. The image you see is 1h of OIII data on the Pacman nebula. I shot 2 minutes subs. However, they all look grayish unless I go below 1 minute, while many astrophotographers can do up to 5 minutes of exposure per sub. Being in B6 surely doesn't help, but I've read that SHO filters should block the majority of light pollution, so I wonder what's the problem.

Imaging train:
Touptek 533M
200/800 mm newtonian

Subs:
120s
316 gain

Conditions:
Bortle 6
40% Moon (had already set)

Can you help me in some way?

[wanton knot]

What was your gain?

[marsh bronze]

316

[marsh bronze]

I was told to switch hgc on, but I doubt it's gonna make that much of a difference, as the subs are already almost overexposed

[tribal briar]

Have you tried imaging a brighter target as a test? Bubble and crescent are both good starters. I don't know what filter you're using, but i'm thinking light pollution is drowning out the target. You can try shorter subs as well. It's also possible that there were some light clouds in the upper atmosphere. Light cloud coverage can hurt it quite a bit. But you're running pretty high on the gain with f4 in a B6 so my guess is too much light getting in.

[marsh bronze]

I can't get enough stars for stacking if I go too low on gain

I might try lower exposures

[marsh bronze]

I did the west veil nebula, which is quite bright, but my image was still washed