Good day! I would disable “Eye Adaptation” or make it more smooth for my space scene. I was reading the documentation “Auto Exposure (Eye Adaptation) | Unreal Engine Documentation”, but I still couldn’t set up the camera.
Maybe someone has encountered such a problem and can help?
Or you could just turn it off in project settings… 
When you use Manual mode for Metering, you need to set the Camera settings in the post process volume to get it working. Enable the Camera settings and adjust those. Then try applying the other settings in the Exposure dropdown.