I tried to shoot an image of Comet C/2020 F3 last night. My settings were ISO 6400, f/5.6 and Shutter speed 2 seconds at 175mm on a MFT camera.
As expected, there is a lot of noise, so I planned to reduce noise by stacking images together using Sequator. Unfortunately, only 6 of the ~25 images turned out to be not blurry/shaky, so the stacked end result is still extremely noisy, especially color noise.
When I turn both luminance and color noise reduction to 100% (!), the noise is reduced a bit, but still very prominent:
This gets even worse when I (try to) set the black and white point in Photoshop:
I've tried reducing the noise using both Photoshop's Reduce Noise filter and the Camera Raw NR, but they do not seem to affect the noise at all. I believe this is because the noise is so large that it is not detected as noise as such.
I will probably try to shoot C/2020 F3 again tonight (if the wheather is clear), but I would still like to process the image that I have.
How can I reduce this noise?