For some reason, I ended up trying this object again, despite it not being really good for my unmodded camera.
I have learned that bumping the exposure time from 90 seconds to 600 won’t help, as long as all the signal gets nonetheless filtered out by the IR filter of the camera.
As you can see, despite the longer integration time, this shot is hardly better than the previous one.
I’d better stick to galaxies and clusters until I get a modded camera. Here’s the previous shot, for reference:
I think the newer one is softer and less noisy, if that’s of any consolation!