How far will a 250 mw green laser go?

A 250mW green laser will have astrength on about 0.25 Luxafter a maximun distance of 68,560 meter (42.6 miles). 0.25 Lux is about the same amount of light a "full moon" will reflect at a clear night to Earth. Normal daylight can vary from 120,000 Lux in direct sunlight to less than 5 lux under thick storm clouds, with the sun at the horizon.