This is probably a silly question, but can some kind person tell me - what is the advantage of having a red light setting on a head torch? Ta in advance.
Yeah, night-vision thing.....however it seems a green light is more effective !
As above, but wildlife in particular don't see red light (some do, many don't) so it is good for watching wildlife without spooking them. Red light is no good for map reading at night as you can't see contours. That's what the green light is for. The drawback to green is that it is more easily seen by people and wildlife than the red light.
Same reason why all sea charts used to be printed only in black and white. Modern ones aren't as good to read under red light.Depends on the individual maps. Aviation charts are generally "red light readable" As are most military maps. Whereas many civilian topographic maps aren't (as you pointed out)