Welcome to Laser Pointer Forums - discuss green laser pointers, blue laser pointers, and all types of lasers



Laser Pointer Store

Why does the beam end in the sky?

SOG

New member
Joined
Jun 13, 2011
Messages
109
Likes
1
Points
0
Oh, and we can use different lens to test it out too... we can even try to zoom into the far side of the beam.

I just read Light Bulbs are Actually “Dark Suckers" um... is that what really happened?
So lasers suck a straight line of dark??

I searched, there seems to be alot of information on the internet about this... I wonder if it's true, but I don't
buy it... Will search for more details later.... but so far I read... if it's follow the theory that light blub
is actually dark suckers, and dark can be sucked away... then it does not explain where "Dark" Came from...
and also why when we look at the "light" it appears to be "Bright"?

Um.. Jesus is the light... so he suck the darkness?
 
Last edited:

Chast

New member
Joined
Jun 15, 2012
Messages
37
Likes
1
Points
0
May be the light go far away,out of your sigt.Or when the light through the air,dust,fog,and other things like that absorb or destroy the molecule.
Personal opinion.:evil:
 
Last edited:

DrSid

New member
Joined
Jul 17, 2010
Messages
1,516
Likes
59
Points
0
As for the beam shots .. you miss several important points.
First .. aperture .. 15cm wont cut it. You need scope as big as possible. IIRC those tests with 2W lasers used 2m telescope.
Next .. filtering and averaging. You only will get few photons back for each pulse. But you also get many other photons .. from air, and even from Moon. You have to filter them by color .. and then do many pulses, and average the brightness curves. That will get rid of the noise, but will amplify the signal.
And that is what simple digital camera cannot do. Also you have to get rid of as much of the sensor noise as possible .. which usually means active cooling.

Detecting laser over large distances can be fun I guess .. but try to 'see' it over few miles first.
 
Last edited:

Dr Stu

New member
Joined
Mar 7, 2012
Messages
1
Likes
1
Points
0
It cant go to the horizon, because if the beam is going staight up, eg normal to the surface, the concept of horizon is meaningless.

So what about my suggestion of using 2 lasers to determine if the beam terminates at the same distance eg at the PBL (post 52)...If you did 1 or 2 measurements at the source (or a few meters away) and a couple of measurements, a mile or 2 away, you could compare the calculated perceived distances between the two different observation points....If the beam appears to stop at the same point ie both calculated distances are the same, you have your answer...:beer:

Edit: Maybe a mile is too much, cos you'd have to take the curvature of the earth into account for the pythagoras calc...maybe 0.5 miles would be better...
I am confused by the notion of "horizon" in this context. I agree with Grainde that it has no meaning. The experiments suggested here should solve the problem though.
 

Blord

New member
Joined
Dec 24, 2007
Messages
5,368
Likes
357
Points
0
Ich verstehe ein bisschen Deutsch :)

They use a multi KW IR laser to create 1600Watt green. Each beam has 400W of green power. The last video is taken from 5Km distance.

It looks like the beam ends in the cloud. It was interesting if they use the laser on a clear sky.
 
Last edited:
Joined
Nov 7, 2008
Messages
5,728
Likes
281
Points
0
I'd say 5km would be suitable for accurate triangulation. Agreed.. if only the cloud cover in the video wasn't there..
 
Last edited:

pixels

New member
Joined
May 3, 2012
Messages
2
Likes
0
Points
0
I think there might be a confusion between "why the beam physically stops," and "why the beam appears to stop."

Obviously, there cannot be a beam if there is little or no material to scatter the light. I think we can all agree that the beam physically stops when the atmosphere stops and/or where the PBL stops.

The point I'm making is the reason why it appears to stop (from the perspective of the pointer user) is the viewing angle - the PBL inherently plays no role in appearance if you cannot even see it. The beam would still appear to stop even if the PBL wasn't present.
Is it only me who finds it painfully obvious that Cyparagon is correct? He is not arguing against the effects of the PBL layer. It's just that trying to see how long a beam is when it originates at arm's length becomes highly ineffective before distances like the PBL layer come into play. Our friend Cyparagon is just saying with a handheld we wouldn't know worth a poop if the visible beam ends at the PBL or hits Zorg the Great in his good eye and saves the known world from alien conquer.

If you live in a city, go up to a tall building and touch it with your hand. Look up. How many stories is it? As hard is it is to tell, it would be much harder to tell if the building were 1cm wide, or a laser beam.

That's fine if you aren't convinced... I just had to get that out of me. Keep the discussions coming.

Edit: haha wow what do you know, after all the lurking my first post was that.
 
Last edited:
Joined
Feb 26, 2011
Messages
191
Likes
2
Points
0
Well just a thought how about put a pointer in the nose cone of a rocket launch it at night
And see if the beam stays the same as we see it standing on the ground.
 




Top