josefran I don't quite understand how to do the flat dark bias.
Just do a Google search for "Flat and Dark calibration frames." Here is an example
https://practicalastrophotography.com/a-brief-guide-to-calibration-frames/
There are better web sites that explain the actual process, but the above should get you started for your further studies.
You must use dark frames with the ASI2600 because the commercial version of the IMX571 sensor has lots of warm pixels -- if you have never seen a raw ASI2600 frame, you will be shocked by how bad it is. So be sure you learn how to use dark frames -- your processing sofware will be able to extract bad pixels from the calibration frame.
With a Bayer camera, if you don't take care of the hot and warm pixels, you will end up with lots of isolated red, green or blue pixels that appear to make small random walks after you stack the sub exposures.
The use of dithering can also help to weaken the appearance of the warm pixels.
Whether you also need to use flat frames will depend on how much your imaging train vignettes, and how dusty your sensor is. If you are going to crop a small galaxy from the center of your frame, and your camera is kept dust free, you pretty much can ignore flat frames.
Dark frames needs the same exposure time as your light frames -- this is so that the dark current build up is the same as the dark current in your light frames. Most processors are able to estimate a dark frame even if it is not taken at the same exposure time as the light frames, as long as you also hand the prosessor a set of Bias frames.
Flat frames can be taken at any exposure level since it is just a measurement of the light falloff.
Chen
