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ArcticMyst Security by Avery
Dot size at 100+m?
- Thread starter vivioo7
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Well, that really depends on the laser's divergence. My 445 has a divergence of 3.57 mrad and has a 5 millimeter beam diameter or should I say width at the aperture. According to some calculations, the bar will be around 36 cm wide at a distance of 100 m. I used this link: pseudonomen137's JScript Laser Calculators to find the divergence and dot size. Hope that answered your question!
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Search is your friend:
http://laserpointerforums.com/f65/dl-spartan-447nm-1-watt-beamshot-dot-400m-1-4mile-54936.html
/insert shameless self promotion
http://laserpointerforums.com/f65/dl-spartan-447nm-1-watt-beamshot-dot-400m-1-4mile-54936.html
/insert shameless self promotion
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Damn, this divergence calculator is extremely accurate. I would get the same "dot" size at that distance!
ZapU
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Just measured my Arctic today. At 310 ft. (94.5M) I measured it at 8 in. (20.3cm) 2.14 mRad
To be honest that calculator is way over my head.
I believe we all have our strengths and weaknesses and trying to figure the dot size is kicking my butt.
What I’m looking for is a way to tell what the dot size will be say at 10 15 feet.
I’m just looking to pick up a laser pointer with a big dot to play with my dog and the little tiny dots get lost on the grass.
Any help?
Thanks!
-Caleb
I believe we all have our strengths and weaknesses and trying to figure the dot size is kicking my butt.
What I’m looking for is a way to tell what the dot size will be say at 10 15 feet.
I’m just looking to pick up a laser pointer with a big dot to play with my dog and the little tiny dots get lost on the grass.
Any help?
Thanks!
-Caleb
The easiest way is too get out there and measure it.
Wrapping your brain around beam divergence isn't difficult. Assuming your beam is Gaussian [ it isn't] a laser with a beam divergence of 1millirad would diverge 1 millimeter for every meter of travel once it passes beyond the Rayleigh Range [length]. With a blue laser like you have there is a fast axis and a slow axis. This means that the beam will expand quicker in one dimension than it will in the other.
Your dog I'm sure will have no trouble seeing the a small dot.
Helios
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A 445nm is not a good dog laser unless you are running it at its minimum threshold which no one does. Get a true 5mW green laser so that theres less risk of your dog going blind from accidental flashes. Green (532nm) is more visible to human eye (dogs too?) so it will appear much brighter than 5mW of 445nm or 650nm etc etc.
If you want a bigger dot just get a focusable laser. Then you can make the dot as wide as a flashlight beam if you wanted to.
Last edited:
DrSid
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With 445 you also must be careful .. the long axis at aperture will be the short one at distance, and vice versa.
Best approach is to disregard aperture size completely, and measure only size at distance (10m at least, better 100m). At such distances aperture size has no effect, and you can also use much simpler formula: divergence=size/distance (both size and distance units must be the same). You really don't need clunky divergence calculator.
Best approach is to disregard aperture size completely, and measure only size at distance (10m at least, better 100m). At such distances aperture size has no effect, and you can also use much simpler formula: divergence=size/distance (both size and distance units must be the same). You really don't need clunky divergence calculator.
