Hi,
This is a hot pixel (one that goes at 100%). A dead pixel is one that stays at 0%. Collectively they are called bad pixels.
I would say up to a few hundred in your whole image is completely imperceptible unless you are looking at 100% magnification so you don't have to do anything about it, especially if you intend to downsample your final image for presentation. Up to 1% (several tens of thousands) can be dealt with modest dithering between subs. There are many reasons why it is a good idea to dither a little (say every 10% of your subs), bad pixels are one of them.
Between 1% and 5% needs either more aggressive dithering a procedure where hot pixels are replaced by the average value of their neighboors, this is extremely efficient and the only "price" is a very small penalty in overall sharpness. PixInsight and Astropixel processor support this procedure by applying a bad pixel map, which is a map of the locations of your bad pixels created using darks and flats. Rawtherapee supports automatic detection of hot/dead pixels in each sub whiile developing the raw file, and it also supports BPM for the difficult cases.
Overall, nothing to worry about unless you have a very small sensor and a very narrow FOV.
This image has more than one hundred thousand hot and dead pixels on each sub and about half of them made it to the integration despite the crazy amount of dithering. See if you can spot them
Cheers,
Dimitris
