Depending on the system you are using there used to be a screen darkening program that worked well with Nobeltec. Since it basically worked in the windows system it did not affect the Navigation software. I personally prefer a darkened piece of plexiglass and some velcro to attach it with. That way I can use the dusk or twilight setting and the computers dimmer to get as low as possible then supplement it with the plexiglass. It can be removed instantly and does not hid items on the chart display as the red or greens do.