see red at night?

lightfoot500 · Dec 4, 2008

Hello,
just got a pretty powerful red.
should i be able to see the beam in the night sky?
this is a smokin 230 mw. couldnt see any beam at all, lucky i am not tryint to point at stars.
my little green 5mw puts up a much better beam for piercing the dark.

thanks.
lf

Things · Dec 4, 2008

The red laser is a much higher wavelength, So while it appears dimmer than the green, it can easily be more powerful. You can usually see the beam at night, but you need to be directly behind the laser to see it properly.

randomlugia · Dec 4, 2008

Or have it aimed at you... Which I do not advise at all. ;D It should be really bright with fog, but green should still be about 4x, if not more bright.

Things · Dec 4, 2008

Thats why I didnt mention it, hehehe

BeavRat · Dec 4, 2008

So if lower wavelength is better, does a blueray have an even more visible ray than green?

Glaserfan · Dec 4, 2008

Green is the most visible color to the human eye. So a green compared to any other laser at the same power will always appear MUCH brighter.

Bluray(405nm) is very near the low end of what our eyes can see. Some of us see it better than others. You will NOT see a bluray beam inside a lighted room for example without smoke or another agent in the air, unless you are looking straight from the laser down the beam. To even see the beam that way you need ~100mW of power.

But when the dot from a bluray hits something fluorescent, you will be amazed! ;D

EDIT: The pic in my avatar looks impressive..BUT that is a ~130mW bluray, mid-foggy night, and 10-second exposure..

lightfoot500 · Dec 4, 2008

thanks for your comments.
i was out with my blu-ray tonite and could see the beam and it looked nice. sort of cloudy outside.
i couldnt see it hardly at all in the house on a cloudy day with blinds half closed, though.

jonrobertd · Dec 4, 2008

Yeah even a 300mw red is nowhere near as "bright" as my 5mw green in open sky (no fog, clouds),
but it is visible at 100 yards. (laser straight up at one end of football field, pal at the other)

ben74 · Dec 4, 2008

jonrobertd said:
Yeah even a 300mw red is nowhere near as "bright" as my 5mw green in open sky (no fog, clouds),
but it is visible at 100 yards. (laser straight up at one end of football field, pal at the other)

My 205mW red is a little bright that my metered 55mW CNI pen out side.

brtaman · Dec 4, 2008

Here is a chart showing relative perceived wavelength dependant intensity to the human eye, notice that the 532nm wavelength corresponds to a much higher value than ~660nm. This represents the reasons behind the differences in intensity based on your what your eyes tell you.

Greenhorn · Dec 5, 2008

brtaman said:
Here is a chart showing relative perceived wavelength dependant intensity to the human eye, notice that the 532nm wavelength corresponds to a much higher value than ~660nm. This represents the reasons behind the differences in intensity based on your what your eyes tell you.

I'm guessing that Y is eye sensitivity. What is X?

Switch · Dec 5, 2008

That's strange, 230mW of red should be brighter than 5mW of green even with a significant difference in diameter. :-? Are you sure it isn't underpowered?

And , actually, without ANY agent in the air, bluray would have the brightest beam ;D

lamborgini8 · Dec 5, 2008

It is harder to see red as said above, but at that power you should be able to see it at night. I can see a beam from a little 80mW red laser at night when its a little foggy.

randomlugia · Dec 7, 2008

Like Switch said, if you shine it through an airless space, blu-ray is capable of ionizing the air particles, while other colors rely on water vapor and stray particles in the air.

Xplorer877 · Dec 9, 2008

randomlugia said:
Like Switch said, if you shine it through an airless space, blu-ray is capable of ionizing the air particles, while other colors rely on water vapor and stray particles in the air.

Blu-ray lasers don't ionize the air. Otherwise you will have a lightning plasma laser.

The 405nm wavelength is small enough to be diffracted off the molecules that make up air (nitrogen, oxygen, CO[sub]2[/sub] ect.). No agent is needed. That is why the sky is blue!

JLSE · Dec 9, 2008

Xplorer877 said:
[quote author=randomlugia link=1228349379/0#13 date=1228620453]Like Switch said, if you shine it through an airless space, blu-ray is capable of ionizing the air particles, while other colors rely on water vapor and stray particles in the air.

Blu-ray lasers don't ionize the air. Otherwise you will have a lightning plasma laser.

The 405nm wavelength is small enough to be diffracted off the molecules that make up air (nitrogen, oxygen, CO[sub]2[/sub] ect.). No agent is needed. That is why the sky is blue!

[/quote]

"An analytical solution based on Maxwell's equations has been developed for UV filamentation in air, arising from a dynamic oscillating balance between self-focusing, diffraction and plasma defocusing. This model suggests that UV (220-420 nm) 200 ps laser pulses with a peak power of around 50 MW (or 12.5 mJ input energy) and a beam size of 100 µm are the optimal tool to trigger outdoor lightning."

-source

http://www.iop.org/ej/article/1367-2630/4/1/361/nj2161.html

To test if your laser ionizes air, place your test leads from a DMM on each side of the beam testing the ohm rating.

*edit/ Or set the DMM to mV, cant remember... Had a customer a while back looking for a laser that could ionize :-? = suicide by lightning :

see red at night?

lightfoot500

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Things

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Things

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lightfoot500

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ben74

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