# How far can they really shine???



## mm85 (Oct 20, 2004)

Thought this would be interesting, who has experimented with distances your dot can actually be seen?

Tonight we did a little experiment to see how far the dot is really going, using my 58mw Wicked pointer and the large white water tower at the edge of our town. I was quite amazed at what I found out.

We started by traveling out to the country, with two others waiting back at the water tower to take pictures. First let me also say that I had used batteries in the pointer(forgot the new E2's) and there was high humidity/mist in the air, but we wanted to get this done. 

Once we reached approx 6.5-7 miles (hard to tell because of the roads) we setup my professional camera tripod on a ridge where the tower could be seen(with the help of it's flashing red light atop) and attached my pointer to the tripod using good ol' duct tape. I called my buddy on his cell and told him to watch as I beamed the tower and had him tell me if I was hitting it good. 

"Wow", is all I heard. There was an approximate 3-4ft green dot visable on the tower he said, and as I stated, visability wasn't on our side. The sad thing is that he got to see it, but his photography skills weren't that great, the pictures he left for me on my cam sucked, badly blurred. 

Anyways just thought you all would like to hear about what our pointers are really capable of, so don't use them in a stupid way! I wouldn't mind trying this another day at around 12 miles with new batts and perfect visability, not to mention getting some good pictures for you all as well.


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## Fussy (Oct 20, 2004)

Hi, i know that this is for a greenie but my normal £1 red laser still goes <1.5 miles!! I think that this is good for a red one!!


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## DaFiend (Oct 20, 2004)

[ QUOTE ]
*Fussy said:*
Hi, i know that this is for a greenie but my normal £1 red laser still goes <1.5 miles!! I think that this is good for a red one!! 

[/ QUOTE ]

1.5 miles = 3.2 kilometers. Hmmmm/ubbthreads/images/graemlins/thinking.gif. All on a Bullet pointer?


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## Fussy (Oct 20, 2004)

yeh, i know, we have a farm house in the country 1.3 ish miles from us so realy its 1.3 as i can hit it and see the dot but it must be a huge dot. You cant see the dot around the farm house as it is grass and woods so it doesnt show up. This is all on a clear night with no fog and we have low humidity but still - im impressed!!


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## mm85 (Oct 20, 2004)

I think it would be really interesting to here about some more instances where the dot could be seen extremely far, so anyone with stories and big lasers please tell all.


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## LASERforLIFE (Oct 20, 2004)

I was playing with my MOD-2 from z-bolt last night.. a TRUE 5mW laser...and i was hitting clouds with it. However, this is my second one and it seems a lot brighter than the first one i had. But i was hitting clouds..you could tell because when it was shined at the sky, the beam just kept going, but when you shined it at a cloud...you could see a point where there was a dot of brightness at the end. I was holding the pointer off to my side so i could see the dot. It was really cool.


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## mm85 (Oct 20, 2004)

As you all probably also know, large green highway signs are like the best long range targets if you want to see what your hitting. My goal is to hit one from 10 miles or more and have someone at the other end. I bet it would be a very bright dot even though it will be large.


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## LASERforLIFE (Oct 20, 2004)

yeah, highway signs are so reflective that it's so easy to see if you're hitting it.


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## Quazar (Oct 20, 2004)

My friend has had reports of his laser being visible from 37 miles. This is with a scanned pattern, not just a straight beam.
It was however putting out 42 watts.


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## sbk (Oct 21, 2004)

With my ~100mW Leadlight, I've seen the dot on a building at about 12km (7.5 miles), it was really clearly visible without optical assistance. 
I can't test it for longer distances because it was the farthest object, but no doubt it will be visible farther...


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## comozo (Oct 21, 2004)

With my Changchun 5mw pointer I have before I modded the optics could see a reflection off a window at 3 miles. After the mod the reflection was brighter. Max so far after one modding of the optics was 13000 feet on a water tank, naked eye. As you have read in my previous posts lower beam divergence = greater distance. For those that live in the state of Maryland this site will be useful for measuring distances accurately. Other states may have something like it. http://www.mdmerlin.net/atlaslaunch.html

It would also be interesting to see photos of the lasers looking directly into the camera at great distances. If you shine it on clouds www.weather.com will give information on the ceiling[cloud height].


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## mm85 (Oct 21, 2004)

Having someone on the other end is nice because you get a report of whats really there, not just what's apparent. 

How can you cut a beams divergence? Is there a way I could go about putting together a simple optics system to lower divergence?


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## Fussy (Oct 21, 2004)

Yes i would also like to know this as i am soon going to buy a laser off maybe abeland1 and would like to know how to lower this down if possible /ubbthreads/images/graemlins/bumpit.gif


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## comozo (Oct 22, 2004)

Page 3 has some info, topic is "laser pointer range extender" There are some more posts deeper in, just look.
read "Sams Laser FAQ". Read about laser beam divergence. You can swap one or both lenses in the pointer.


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## DaFiend (Oct 22, 2004)

it may be more appropriate to post a Link to that thread instead of the page number./ubbthreads/images/graemlins/thumbsup.gif Sooner or later thats not gonna be on page 3...... /ubbthreads/images/graemlins/smile.gif


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## comozo (Oct 22, 2004)

The 2 lenses that can be swapped are the diverging lens and the collimating lens. The easiest is the collimating lens.
Whether you have a Leadlight or a Changchun the collimating lens most likely has a focal length of 15-18mm. So a longer focal length lens is needed. The combinations are:
1 Plano-convex[ I like AR coated lenses] 12mm diameter.
2 Plano-convex + a Plano-concave 
3 Plano-convex + a Double-concave
A wide variety of lenses can be bought from Edmund Industrial Optics. Measure the inside diameter of the casing to make certain a lens of that diameter will fit. 
link 
http://www.edmundoptics.com

Page link http://www.candlepowerforums.com/ubbthreads/showflat.php?Cat=&Number=719894&page=2&view=collapsed&sb=5&o=365&fpart=1


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## mm85 (Oct 22, 2004)

Well I just ordered the lens set and plans from Amazing1.com. As soon as I build it, I'm going to try this experiment again, only way further away. 

This lens set will cut divergence by a 7 factor. So given that my buddies saw my dot at 7 miles easily, theoretically that same dot could now be witnessed at 49 miles. I don't know what you guys think, but this sounds damned amazing to me.


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## aussielextsy (Oct 23, 2004)

so by cutting divergence what changes in the laser. i know you can see further but what are the negative aspects? is it not as bright or thinner line?


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## mm85 (Oct 23, 2004)

Divergence will cause your beam to spread over a distance, therefore becoming more like a weak flashlight rather than a laser. If you can hold your beam in a tight line the light will have more apparent visability further away.

Now for my question, what limits how low you can get your divergence?


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## Fussy (Oct 23, 2004)

i would think nothing would limit it? what about the focus lense couldnt you just turn that to a focal infinity thing? instead of it bieng close?


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## comozo (Oct 23, 2004)

One thing to note is that the "focus lens" is not focusing it is Collimating, Forming a column of light, with a particular divergence.A more accurate term is Infinite Conjugation. Take for instance the lens in your pointer. By moving it out you'll see that the beam grows wider, dimmer with distance, you can make the beam so wide as to become to dim to see, and by moving it closer to the diverging lens you can focus the beam producing a bright spot at close distance [few feet]]. At some point in between, the beam will have optimum collimation. Expanding the beam before it is collimated will keep the sides of the beam closer to paralell over a greater distance. There is no limit to lower divergence except you can't have 
Zero divergence, this if it were possible means the sides of the beam remain paralell to each other forever. The negative side is if you were to expand the beam to a high degree I'm talking inches or centimeters in diameter or more then the beam would appear dimmer a distance cause the energy has been dipersed over a greater area. This should not be a concern with pointers for the maximum diameter lens is around 12 millimeters. I'm not an expert in this matter. I'm saying this by way of practical experience and reading.


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## comozo (Nov 1, 2004)

I thought this was interesting.
"This is sweet!! 
If these lasers are the power as advertised they will be 
very bright! 
Craig if I may call you Craig? 
You will have fun aiming them at Ocean or river bouys they have reflective tape all over them.. 
For super distance I have a retro-reflector I put on the Washington side of the Columbia river 12 miles across, 
I can light up my back wall with the bounced back laser energy... 
I have been trying for some time to hit the retro`s on the moon, no luck yet."

This can be found a this link: http://www.candlepowerforums.com/ubbthreads/showflat.php?Cat=&Board=UBB3&Number=216561&page=1&view=collapsed&sb=5&o=&fpart=1


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