Bit of a side track
The USAF did a complete survey on things such as, cockpit lighting, meals before and during flights, rest periods before and during flights etc.
The published result regarding night flying was that, in the cruise, the cockpit should be as light as possible as this can reduce fatigue by as much as 75%.
At night, unless you are actually focused on an object then your eyes focused range is about 9 inches, 22.8cms on the other side of the cockpit glass.
Flying in the cruise, at night, with a darkened cockpit is not recommended.