visibility of beams versus viewing angle/distance

[zamane]

I am curious regarding the visibility of a green laser beam with a long-distance focus ie more or less parallel beams. I know that especially for green lasers with power greater than 50mW or so, the beam is very visible in low light conditions, but this is from the holder's point of view. How visible would the beam be from an onlooker who is say 300 meters (1,000 ft) away from the beam and has a 90 degree viewing angle (looks perpendicular to the path of the beam). How visible would that be? Would it still be as strong ? Anybody looked at a green laser beam from a distance before (provided that the beam was not directed at them) ?

 

[jonasa0601]

Re: visibility of beams versus viewing angle/dista

With 50mW it wouldn't be so visible.. I don't think people will notice it unless they scout for a laser beam.

 

[a4rings]

Re: visibility of beams versus viewing angle/dista

I had a novalaser alpha 65mW at this time (until I broke it and got a 105mW) I was pointing it in the sky and a friend came over and said that they could see the beam while driving to my house. and he was a few streets away.

 

[Warske]

Re: visibility of beams versus viewing angle/dista

I had a novalaser alpha 65mW at this time (until I broke it and got a 105mW) I was pointing it in the sky and a friend came over and said that they could see the beam while driving to my house.  and he was a few streets away.  

Impressive. Was there fog, smog, or rain? Or was it clear?

 

[iskor12]

Re: visibility of beams versus viewing angle/dista

I currently on have a 15mW green laser and I have tested out exactly what you are asking. It is visible untill you hit about 75 feet away from the laser beam.

 

[RA_pierce]

Re: visibility of beams versus viewing angle/dista

I've found that about 100mW of green pointed vertically into the sky on a clear night is:

Very visible up to 40 feet
Fairly visible up to 80 feet
Slightly visible at 120 feet
Unnoticeable beyond 130 feet

On a good night when clouds are low the dot can be seen on the clouds pretty well.
When the "spot" on the clouds is viewed from a distance, you can see that it isn't really a "spot." It looks more like what you would expect to see if you directed your laser's beam through a puff of smoke or steam from a distance.

Beam from ~20 feet

Beam from ~80 feet

 

[a4rings]

Re: visibility of beams versus viewing angle/dista

[quote author=A4RINGS link=1239884274/0#2 date=1239889112]I had a novalaser alpha 65mW at this time (until I broke it and got a 105mW) I was pointing it in the sky and a friend came over and said that they could see the beam while driving to my house.  and he was a few streets away.  

Impressive.  Was there fog, smog, or rain?  Or was it clear?[/quote]

It was clear out. Nova lasers are so incredible. wish they would make other colors other than green, want more!