A friend and I would like to try communicating (Morse code signaling) with off the shelf laser pointers from two hill tops (~350m above sea level) separated by about 16km. It would be nice to do this without binoculars but I’m not sure if that is possible with readily available off the shelf laser pointers. 5mW lasers are easiest and cheapest to acquire, however, I can go higher since this is not regulated where we will be. My basic question is: what wavelength and power laser pointer would work over this distance while trying to contain the cost? Our main concern is the haze due to pollution and humidity which is the norm in the place that we want to try this but we would do it on a day where we could at least see the outline of the hills from 16km – though, perhaps, not individual features. I understand that the human eye is most sensitive to green (555nm) but suspect red lasers (650nm) would propagate through atmosphere better due to less Rayleigh scattering (but I have not been able to verify for this laser application). As for the power side of the question, obviously the more the better but then cost starts to become a factor. From what I’ve seen red lasers are cheaper due to their simplicity so I could get a more powerful one for less. I'd like to do this with the least power for any chosen wavelength, though. In trying to find out what sort of attenuation I'd be up against, I googled for phrases like “atmospheric effects on propagation of laser light” but didn’t turn up much for the wavelengths of standard laser pointers. Most of the literature was about communication equipment that seems to be set around 785nm and 1550nm. I tried to read some of those papers to see if I could glean anything but I haven’t looked at any real physics in 20 years so it was difficult to parse. Any suggestions would be greatly appreciated.