I am using the BlackMagic Pocket Cinema Camera (original) to play around with capturing images of the night sky.
So this is a Super16 2.1MP sensor with a 135mm cinema lens at T2.2 capturing 12-bit color RAW images at 24 images per second and 360 degrees of shutter angle.
If I up the exposure of the captured image in post then I get an image with thousands of different coloured points of light.
Are these stars or noise?
The correct answer is probably "both". What I would recommend is to take two consecutive photos and compare the output. This is going to be difficult because the earth is turning and the stars' relative position will change (rotate) as well as translate across your photo. If you mounted it on a sky tracking telescope mount it would be easier to make the comparison.
Another perhaps more simple method is to use a longer exposure. Stars will then be slightly streaked, and noise will not streak, so you can see how much, in general, your photos are including noise.
From my own experience in sky photography, there is almost always some noise. Sharpening brings it out. The best way to remove noise is to use multiple exposures on a calibrated tracking platform and use software to remove the points that only appear in one image.
It's not an easy question to answer precisely other than to say yes some of those points are most certainly noise because even in very expensive cameras there are some noise points. It is also highly certain that not all of them are noise. There are a lot of stars in the sky and many that you cannot see with the unaided eye so it is not surprising that a photo will reveal more than you can see.
It is mostly colorful noise.
This can be deduced by upping the gain on the image in post on a frame captured during an accidental rapid movement of the camera.
Everything that stays “in focus” is noise.
With this in mind I re-processed the image and this is is about as clean as I could get it:
