astrophotography dof circle of confusion

[dansawyer]

The camera is an EOS M1 and the application is astrophotography. After several attempts I have the basic operations in place and astrophotography is working. There is a remaining question; DOF settings remain active and there is a settable variable remaining "Circle of Confusion". The value is in um. The camera is in manual mode and the focus is set to infinity. Exposures are long, typically 30 to 90 seconds. The range of values are 1 um to 100 um.
In this case what is the effect of changing the Circle of Confusion value in astrophotography?