100mw distance

[payj]

Ok so as a kid I had one of those cheap $30 laser pointers and I remember you could shine them pretty far. I would say the length of 3-4 footballl fields maybe further, if it was pitch black out in the city. At that range maybe a little further you could see a faint red dot on a building. My question is how far will a 100-110mw shine visibly? If I had a set of really nice binoculars could I see a dot on a building or other object very very far away?

thanks,

Justin

 

[shreknow91]

are you talking about red or green lasers?

 

[Cxrazy]

A green 100mw is pretty darn far...

I've heard stories of people going to the mountains in CO and putting the laser on a tripod and shining it towards their friends on another mountain a few miles away, and remember them saying that the dot was HUGE.

;D Urban legend? Myth? I'll never know until I go to CO and try it myself.

 

[xXlaser_fanXx]

theres to many variables to give 1 answer but the averages ive seen for a good 100mw green is around 30-40 miles

 

[wooooooolazer]

technicaly it will go on forever, it will just be a continualy bigger dot, as far as how far you could see it, that would be a pretty long ways away, say if you were like in an ocean im sure it would be visible 20miles away to another ship, it would only be stopped by the curvature of the earth.

...lazer.... ;D ;D ;D

 

[Krutz]

the important thing is the beamquality (=divergence), not the power. they could see a he-ne laser shining from the earth up to the spaceshuttle back then. dont remember the output, but perhaps 5 to 20mw, red that is. and going through all kinds of weird atmospheric layers too.
a pointer with a decent beam will shine further than you can see. even a regular red one, i would say.

dont point it on airplanes, please. pretty please.

manuel

 

[wooooooolazer]

yes, if you ever see flashing lights in the sky its not good to point at them.... even tho when the laser hits the plain it will be 4 meters big and be the same as just a flaslight, but they still will be freaked out and think some maniac is trying to burn down the plane or something by using a green death beam.

...lazer.... ;D ;D ;D

 

[Chief-Eamonn]

longer than youll ever need basicly

 

[likewhat]

I remember in undergrad optics we did a calculation that if you shine a laser that is 2mm starting beam size by the time it got to the moon it would be bigger than the moon. If you want to shine it really for for some reason you have to start with a big beam diameter.

 

[darklandz]

i could shine my old 15mw green pointer on a school which was just under a mile away from the aperture and u could clearly see the dot hitting the target.
no idea what the actual size of the dot was on the target, but as mentioned above - it probably wouldve been HUGE.

 

[payj]

the one as a kid was red. The one I was looking at is green. Specifically the nova x105. So it will definatly put a dot of some size on a bilding a few miles away right? Lol one could get themselves into allot of trouble with o e of these. Does anyone have a story to tell lol?

 

[Switch]

I remember in undergrad optics we did a calculation that if you shine a laser that is 2mm starting  beam size by the time it got to the moon it would be bigger than the moon. If you want to shine it really for for some reason you have to start with a big beam diameter.

Beam diameter has little relevance, divergence is the key.

Anyway I remeber dragon lasers claiming that their 300mW Spartan can reach Mars, so a 100mW laser would go 1/3 the distance to Mars (I love dissing stupid advertising)

I don't think that a laser dot would be bigger than the moon by the time it reaches it, it can't be.When you shine it at te moon it looks like a thin line....It can't diverge that much that fast, can it? :-/ Have to make some calculations....

Btw, they don't make the X-105 anymore, it's called the X-100 now, but as they were tested, they're the same lasers as the old X-105s.

One thing those high powered lasers are good for is scaring crows off buildings far away, thats fun

 

[likewhat]

Beam diameter has little relevance, divergence is the key.

Uhh, you might wanna think about that for a second. The divergence of a beam is dictated by the wavelength and the minimum spot size.

http://en.wikipedia.org/wiki/Gaussian_beam

 

[Switch]

All I'm saying is that you can have a big beam diameter and still have crap divergence.....

 

[payj]

hmm I just ordered my "x105" it says so on their website, I guess they haven't updated it. I havent heard anything but good things about Nova so I should be happy?


back to my question though...In your guys gals educated guess, how big of a dot would it put on a building lets say 2 miles away?

 

[Switch]

X100 Compact Portable >100mW Laser w/carrying case, NOVA Membership, 1145 LightYear Reward Points

Price USD229.00

Discover our X-Series compact portable high powered green lasers. Perfect for both beginner and advanced laser enthusiasts.

Where did you order it from??

By my calculations, considering 1.2mRad divergence claimed on the site, your dot would be 3.85 meters (thats about 12.5 feet) across on a building 2 miles away.