Have you ever wondered what ISO you should use for astrophotography. Turns out it is not a simple answer. Figures right? Astrophotography has to be so difficult. There is a science to it though, and that is the good news.
This website has some helpful charts.
This one bellow is for the dynamic range. From this you can see what your dynamic range will be for a particular ISO.
https://www.photonstophotos.net/Charts/PDR.htm
And this link shows the Read noise in e.
https://www.photonstophotos.net/Charts/RN_e.htm