A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: Frank Reed
Date: 2018 Jun 13, 14:13 -0700
You can, of course, look directly at a laser from great enough distance. Coherent light isn't brighter than other light.
There was a fun experimental demo of this some years ago. An amateur astronomy group used searchlights to signal astronaut Don Pettit aboard the ISS. They also aimed a blue laser (800 mW) at the station, and Pettit was able to see both the searchlight flashes and the blue laser. Space stations are fun! Some details:
I was surprised to learn at laserpointersafety.com that the "nominal ocular hazard distance" (in plainer words, the "low-risk quick peek" distance) for an 800 milliWatt blue laser is less than 500 feet, and the FAA glare distance is less than three nautical miles. I would have expected distances ten times greater...
I do wonder if astronauts on the Moon could hypothetically see the laser pulses used for the laser-ranging experiments. Given that the beam spreads to about a kilometer at that range, I doubt that there would be anything visible under normal conditions even with the high-power focused beams used for laser-ranging. The beams surely wouldn't be bright enough to cause any eye damage at that range, right?