Focus watchdog..please share your knowlgede


I do use the auto focus routine successfully during the night. I refocus every 1 degree temp change.
I have not yet set my auto focus watchdog as I am not sure which values are the right ones to use.

I image at 650mm FL at 1.19 "/ pixel.
What would be the appropriate HDF to use ?

Any other hints how the system can monitor the right focus over the course of the night ?

Thank you very much