@mike@kev my brother-in-law could see them in Canada with a 5 second exposure but not by eye. The shots I posted were 3 second exposures so brighter than by eye, and you couldn't see the blues by eye at all, but the red and some of the green & yellow were very visible. We'd driven to a darker spot just up the road but even from our house with surrounding streetlights and such the red was still very visible by eye.