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ArcticMyst Security by Avery
Average Distance of lasers
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Speedy78
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This is a very hard question to answer. Are you loiking for how far you can see it or it can be seen from the other end? Im sure if you were on mars with a telescope and you were zoomed in on me on earth and I shined a laser at you you would be able to see it.
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I can say that an experiment was carried out on the International Space Station, in which a 1W 445nm laser on earth was not only measured, but visible to the eye(IIRC). There is a wiki article somewhere on it, as well as a NASA link on it.
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This thread:
http://laserpointerforums.com/f44/amateur-astronomers-flash-space-station-1w-blue-laser-72271.html
Also, my and a friend tested a 2W 445nm laser with a G2 lens and the beam was visible pointed about 45 degrees overhead at approx two miles. I know that with a super Long Focal Length lens that it could travel further and remain as a beam. At some point you are relying on pure output power rather than beam divergence because of the Rayleigh effect. From what I have seen the longer the wavelength the better the beam will travel and this is confirmed by the rayleigh effect. So in other words, a red laser(650-660nm) will travel extremely well but will require much more power to produce a visible beam as opposed to a 445nm laser which quite easily produces a beam but will scatter out and lose its dot and beam much quicker.
EDIT: Awe damn, I killed my L33T post number XD.
http://laserpointerforums.com/f44/amateur-astronomers-flash-space-station-1w-blue-laser-72271.html
Also, my and a friend tested a 2W 445nm laser with a G2 lens and the beam was visible pointed about 45 degrees overhead at approx two miles. I know that with a super Long Focal Length lens that it could travel further and remain as a beam. At some point you are relying on pure output power rather than beam divergence because of the Rayleigh effect. From what I have seen the longer the wavelength the better the beam will travel and this is confirmed by the rayleigh effect. So in other words, a red laser(650-660nm) will travel extremely well but will require much more power to produce a visible beam as opposed to a 445nm laser which quite easily produces a beam but will scatter out and lose its dot and beam much quicker.
EDIT: Awe damn, I killed my L33T post number XD.
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To infinity and beyond or until it's scattered to below detectability or is stop by some solid object. There is no average distance do to a large number of variables
ktroy
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I do wonder how far it can be seen from an observing standpoint.
For example, car headlights can be seen on roads miles and miles away from a good vantage point, even when the headlights are not aimed at the observer. (cars traveling on a distant interstate)
Also think blinking lights on cell towers and such. You can see those for 20 miles even more.
So putting this into perspective, I do wonder how far and how bright a laser would be aimed at somebody miles away on a mountain or something. Away from city lights I have to believe it would be quite piercing from even a rather modest 20mw or so green.
For example, car headlights can be seen on roads miles and miles away from a good vantage point, even when the headlights are not aimed at the observer. (cars traveling on a distant interstate)
Also think blinking lights on cell towers and such. You can see those for 20 miles even more.
So putting this into perspective, I do wonder how far and how bright a laser would be aimed at somebody miles away on a mountain or something. Away from city lights I have to believe it would be quite piercing from even a rather modest 20mw or so green.
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I suppose you will need to get a 1 Watt 445nm Laser to
do the tests you describe yourself and report your findings
back to us...
Then we can point any other new member to your findings.:beer:
Jerry
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Well they did shine a 1W 445nm at the International Space Station and the Astronaut could see it... Basically, it sounds to me like it can by the target for such a long distance it doesn't matter.
Also, different wavelengths would act differently. A red(638-660nm) laser would likely attain a similar result with far less power.
Also, different wavelengths would act differently. A red(638-660nm) laser would likely attain a similar result with far less power.
ktroy
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Dadg Apex, you have quite a selection of lasers there. I like the 638nm you mentioned, they are so much brighter than 650nm. I didn't know they have less light scatter though.
lasersbee, please feel free to send me a laser for "testing purposes" and I will post results. There's actually some summer homes on the mountain next to me that I shine my low power pointer at sometimes. With binoculars I can see them on the deck shining flashlights back and flashing their indoor lights on/off. I do wonder how bright the laser was to them.
lasersbee, please feel free to send me a laser for "testing purposes" and I will post results. There's actually some summer homes on the mountain next to me that I shine my low power pointer at sometimes. With binoculars I can see them on the deck shining flashlights back and flashing their indoor lights on/off. I do wonder how bright the laser was to them.
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Dadg Apex, you have quite a selection of lasers there. I like the 638nm you mentioned, they are so much brighter than 650nm. I didn't know they have less light scatter though.
lasersbee, please feel free to send me a laser for "testing purposes" and I will post results. There's actually some summer homes on the mountain next to me that I shine my low power pointer at sometimes. With binoculars I can see them on the deck shining flashlights back and flashing their indoor lights on/off. I do wonder how bright the laser was to them.
Lol, that's not all my lasers either. 638nm lasers are brighter but they don't scatter less than 650nm. Actually 650nm would scatter a small amount less. Here is a little diagram showing the effects of Rayleigh Scattering on sunlight which can give you a good idea as to what happens with various wavelengths:
Also, please avoid shining lasers at people or where people are. That type of thing is also partly the cause of laser laws. Even if its not actually dangerous clearly it was bothering them.
ktroy
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Thanks for the graph, that's good to know.
as for the shining, I only did it for a moment, and they rather enjoyed it by flashing back and signaling to me. At least that's how I interpreted it, They were just waving flashlights and having a good time.
True though, it's not advisable even with low powers.
as for the shining, I only did it for a moment, and they rather enjoyed it by flashing back and signaling to me. At least that's how I interpreted it, They were just waving flashlights and having a good time.
True though, it's not advisable even with low powers.
ARG
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My avatar was only 80mW (or so) of 473nm and that was 1km away.
At long distances what it really depends on is how far away the person viewing it is from where the beam terminates. If they are within 20m they can see it, but if they are 50m or further away they can't see it.
I'm going back to the place where said photo was shot, I will try and get some video of different lasers over long distances to show the effect. I may bring my projector for this purpose.
At long distances what it really depends on is how far away the person viewing it is from where the beam terminates. If they are within 20m they can see it, but if they are 50m or further away they can't see it.
I'm going back to the place where said photo was shot, I will try and get some video of different lasers over long distances to show the effect. I may bring my projector for this purpose.
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Lolvo
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Looking at my 445nm lasers from a distance, you can see the beam, but the color is dull, almost like a blue-ish grey.
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When I go camping, if time allows I will attempt some long distance extreme dark visual tests. I am taking along my G2, LFL, and a 3-Element on a 2.65W(on a G2) 445nm M140 build I have. Off the bat I know the LFL is going to win since its divergence is superior to any of the other lenses.
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lasersbee, please feel free to send me a laser for "testing purposes" and I will post results. There's actually some summer homes on the mountain next to me that I shine my low power pointer at sometimes. With binoculars I can see them on the deck shining flashlights back and flashing their indoor lights on/off. I do wonder how bright the laser was to them.
As you stated here it seems that you already own Lasers and
don't want any that are over 15mW because of understandable
inexperience fear.....
http://laserpointerforums.com/f50/can-anybody-build-me-15mw-635nm-pointer-81202.html#post1166045
You can easily do your Max Range test with the Lasers you
already own and report back here.
Besides the Lasers we have in the shop are way over the
maximum 15mW....:beer:
Jerry
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Have always found it odd that a lot of the companies selling lasers list a distance.
