Other things you can do to clean up the image:
In astrophotography Along with taking a dark, cap-on, photo of the same length with the same settings to subtract from your actual image you can also take a "twilight sky flat". This can compensate for pixels on the sensor that are more or less sensitive than others. A description of the process can be found here: https://physics.bgsu.edu/~layden/ASTRO/OBSERVATORY/obs_instr_skyflats.htm
Another thing you can do, though I'm not sure off-the-shelf cameras have the ability, is take a bias image/frame, or a picture of no exposure time. This will let you subtract the noise of the sensor itself. I think the best you could do is, with the cap on, take a picture of the shortest exposure you can.
Another resource: https://practicalastrophotography.com/a-brief-guide-to-calibration-frames/