deSitter
Pooh-Bah
Reged: 12/09/04
Posts: 1079
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..is to the owner! Should an airplane fly through the beam, you could be in deep doo-doo under the Patriot Act:
http://www.msnbc.msn.com/id/6775100/
Bad idea all around, IMO.
-drl
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rmollise
Carpal Tunnel
Reged: 07/06/07
Posts: 2048
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Quote:
..is to the owner! Should an airplane fly through the beam, you could be in deep doo-doo under the Patriot Act:
http://www.msnbc.msn.com/id/6775100/
Bad idea all around, IMO.
-drl
Unless you live near an airport, and are pointing up in the glide path, the chances of:
1. This happening.
2. And someone aboard the aircraft noticing.
Are vanishinly small. This incident happened three years ago, and it's obvious the guy was very much trying to cause trouble. IOW? You will have to work and work hard to get yourself in trouble this way.
I have been using a green laser both with my university astronomy students and at star parties where I am a speaker--when I'm called upon to do "sky tours"--for years and have yet to have any black helicopters land in my backyard. Hell, I can't even spell "Gitmo."
Certainly anyone using a green laser should be responsible and careful. But "the gubmint might come get you" is no reason to give in to a Nanny State mentality and stop using a useful AND LEGAL tool.
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Uncle Rod
Rod's New Book:
Choosing and Using a New CAT
Available now!
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steveoid
sage
Reged: 02/10/08
Posts: 468
Loc: London,England
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Having just bought a 5mW laser I used it for the first time last night attached to my large binoculars. The beam was excellent for locating objects where pointing a large 90 degree viewing angled binocular and finding an object is almost impossible. I looked very carefully into the part of the sky where I was going to point just to make sure there were no aircraft near. It’s a fine piece of kit and I will be responsible on its use when I am out observing. Steve
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Celestron C8
120mm ED Pro refractor.
80mm ED Pro refractor (solar observing)
Baader Herscel wedge.
Quantum 6- X20,X30 & X37 100MM binoculars.
Helios 10.5 x 70mm HD binoculars
Heq5 Pro mount.Eye pieces
Celestron ultima 2x barlow.
FR/FC lens 6.3 Celestron.
2" WO Dielectric.
Hyperian eyepieces.
Vixen lanthamum eyepieces.
Watec120n+ ccd camera.
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GeorgeDuke
Pooh-Bah
Reged: 04/24/03
Posts: 1260
Loc: PARADISE! (So.Florida)
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I would like to get a real answer from someone who knows.
How far does a beam from a 5mw green laser actually travel.
I know it looks like it travels right up to Jupiter etc. but that is an illusion.
From what I have been able to gather, the beam actually travels about 1,000 feet or so. I know there are high powered lasers available but the 5mw is all we need for our Astronomy use so let's stick with that.
As Ron said above, unless you are at the airport, or at the top of a skyscraper, or in another airplane, you can't even see the pilot unless he leans out the window to look down at you. And then I doubt if the plane would be low enough.
Most new devices invoke panic in a segment of the population until they become omni present.
There is also a fear among imagers that a laser beam will ruin one of their images.
I read somewhere of tests done and it was not possible to get the laser beam to appear in one of the deep sky images. In fact pointing the imaging scope right at the person using the laser they could not get a picture of the beam without combining multiple images.
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George
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SkyShed POD XL-3
LX200GPS 203mm f10
StellarVue SV102ED2 Feathertouch Ser#0018
LXD75 GOTO with Orion 16" pier extension
Baader Hyperion 8mm ,13mm, 21mm and 8-24mm Zoom + FTRs
2" GSO ED barlow, Orion 2" Prism Diag. 2" SV Dielectric
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Midnight Dan
scholastic sledgehammer
Reged: 01/23/08
Posts: 840
Loc: Brockport, NY
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How far does a laser travel? There's no one answer to this. Yes, it depends on the power of the laser (and the condition of the batteries). But even more important is the quality of the sky. The more particulates, humidity, etc. the more light will be absorbed and scattered. On a good clear, stable night, it can travel a VERY long distance.
Keep in mind that how far the beam is visible by you, is a very different thing from how far away you'll see it if it's aiming at you. Think about car headlights. When you're driving a car at night, your headlights will not illuminate the road very far in front of you. But people coming at you in the other direction can easily see your headlights over a mile away.
Same is true for the laser. The beam may not be visible for more than a thousand feet or so, but it can still be blinding bright for a VERY long way beyond that to someone looking at it.
-Dan
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Scopes: Celestron NexStar 8SE, Orion EON 72mm ED/APO, Orion ShortTube 80
Mounts: NexStar Alt/Az GoTo, Orion Astroview (EQ3) w/single axis drive
Eyepieces: Baader Hyperion 21mm 13mm, 8mm, 5mm; GO 32mm SWA;
Other: 2x & 3x Barlow, 0.63x Focal Reducer, Dew-not strips, DewBuster controller
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Jason D
Carpal Tunnel
Reged: 10/21/06
Posts: 2067
Loc: California
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Quote:
Same is true for the laser. The beam may not be visible for more than a thousand feet or so, but it can still be blinding bright for a VERY long way beyond that to someone looking at it.
True...
But let us do the math...
If someone shines a 5mW laser beam at someone's eye with 7mm eye-pupil standing 1000 feet away, then the person holding the laser has to hold his/her hand steady within 2.5 arc seconds tolerance for at least 1 minute to cause permanent eye damage. If human hands can be this steady then who would need a scope mount.
Jason
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XT10 classic with premium optics
Tri-knob CR2 with compression rings
Round Table Platform
4.5" StarBlast
6" StarBlast6
TV EPs
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denodan
professor emeritus
Reged: 10/06/04
Posts: 596
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Also the laser beam will not remain a tight narrow beam, it accually increases in size the further it goes, the light spreads out, so at 1 kilometer, or so,the dot maybe the size of a tennis ball,etc, the further the beam the more the dot will spread.
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KDizzle
member
Reged: 09/12/08
Posts: 66
Loc: Woodinville, WA
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The laser collimation also comes into effect. The Zhumell laser poitner I have diffuses quite a bit over distance. So muhc so that when measuring from about 100 feet away, the size of the green 'dot' that it creates is actually about 2 inches diameter! Ironically this is good because when you are 100 feet away, trying to see a dot the size of a pea is also not so easy. I don't know how much it diffuses over 1000 ft, but I could only iamgine that it becomes much more diffused - a dot with a diameter over a foot wouldn't be too unexpected imo.
Here is a picture of the dot from about 40 feet away; clearly it is half an inch diameter, eh?
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walt r
Carpal Tunnel
Reged: 02/13/07
Posts: 2579
Loc: Doylestown, PA
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A very low power LASER can be seen from quite a distance when the beam is directly towards you. Many years ago for a communication experiment a 1mW HeNe LASER was set up on the roof of a university building (I think it was in Phoenix) and aimed at the universities observatory 20+ miles away. When the researches arrived at the parking lot the LASER was the brightest light on the city skyline and the beam had spread to several hundred feet wide.
LASER diodes are not as well collimated (beam divergence is greater than a gas LASER) but it is still quite bright to look at from many miles away.
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Walt
Obsession 18" f/4.45 #1370 AN/SC
MK67 Deluxe 6" f/12 Mak-Cass, Super Polaris GEM, JMI MicroMax DSC
DIY 60mm f/6 Achromat
Cookbook 245 CCD
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deSitter
Pooh-Bah
Reged: 12/09/04
Posts: 1079
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Quote:
I would like to get a real answer from someone who knows.
How far does a beam from a 5mw green laser actually travel.
I know it looks like it travels right up to Jupiter etc. but that is an illusion.
From what I have been able to gather, the beam actually travels about 1,000 feet or so. I know there are high powered lasers available but the 5mw is all we need for our Astronomy use so let's stick with that.
As Ron said above, unless you are at the airport, or at the top of a skyscraper, or in another airplane, you can't even see the pilot unless he leans out the window to look down at you. And then I doubt if the plane would be low enough.
Most new devices invoke panic in a segment of the population until they become omni present.
There is also a fear among imagers that a laser beam will ruin one of their images.
I read somewhere of tests done and it was not possible to get the laser beam to appear in one of the deep sky images. In fact pointing the imaging scope right at the person using the laser they could not get a picture of the beam without combining multiple images.
Well I didn't mean to imply panic, other than what the gov't will do to you in case of a harmless accident. I do in fact live right under the busiest waypoint on final approach to the busiest airport in the country, so any laser activity at night is out of the question.
Actually when it comes to teaching people the constellations, I've never had any problems just pointing out the stars with my 0-watt fore-finger.
-drl
-drl
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New Mexico Craig
sage
Reged: 09/05/07
Posts: 226
Loc: The Land of Enchantment
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Quote:
Actually when it comes to teaching people the constellations, I've never had any problems just pointing out the stars with my 0-watt fore-finger.
LMAO! Good point (literally)! 
craig
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Celestron CPC 1100 (aka "the groove tube")
The Motto of the Solar System :"Id quot circumiret, circumveniat."
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Dipole
sage
Reged: 12/21/06
Posts: 398
Loc: Right behind you
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Ok, I did a test...
I pointed my 5mW green laser pointer to the horizon directly West. My buddy swears he saw a dim green spot on the back of my head.
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Midnight Dan
scholastic sledgehammer
Reged: 01/23/08
Posts: 840
Loc: Brockport, NY
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 Well that does it! I've had my good laugh for the day!
-Dan
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Scopes: Celestron NexStar 8SE, Orion EON 72mm ED/APO, Orion ShortTube 80
Mounts: NexStar Alt/Az GoTo, Orion Astroview (EQ3) w/single axis drive
Eyepieces: Baader Hyperion 21mm 13mm, 8mm, 5mm; GO 32mm SWA;
Other: 2x & 3x Barlow, 0.63x Focal Reducer, Dew-not strips, DewBuster controller
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deSitter
Pooh-Bah
Reged: 12/09/04
Posts: 1079
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Quote:
Ok, I did a test...
I pointed my 5mW green laser pointer to the horizon directly West. My buddy swears he saw a dim green spot on the back of my head.
ROFL - yeah but was it warm?
The temptation to play Luke Skypointer would be too great I think and beams would be flying.
-drl
Edited by csa/montana (09/22/08 06:35 PM)
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New Mexico Craig
sage
Reged: 09/05/07
Posts: 226
Loc: The Land of Enchantment
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Post deleted by csa/montana
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Celestron CPC 1100 (aka "the groove tube")
The Motto of the Solar System :"Id quot circumiret, circumveniat."
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rmollise
Carpal Tunnel
Reged: 07/06/07
Posts: 2048
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Quote:
Actually when it comes to teaching people the constellations, I've never had any problems just pointing out the stars with my 0-watt fore-finger.
-drl
-drl
If you put your forefinger to good use, more power to you. For most folks, even living near airports, laser use is completely safe, and is much more effective with large crowds at dark sites than the Fickle Finger of Fate.
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Uncle Rod
Rod's New Book:
Choosing and Using a New CAT
Available now!
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cam1936
sage
Reged: 08/01/08
Posts: 244
Loc: Alberta, Canada
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Quote:
..is to the owner! Should an airplane fly through the beam, you could be in deep doo-doo under the Patriot Act:
http://www.msnbc.msn.com/id/6775100/
Bad idea all around, IMO.
-drl
Guy tried to blame it on his daughter. What a coward.
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C8-SGT
Nikon 10x50 Action Ex
Canon 350D
Manfrotto tripod
Various EPs and accesories
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Jason D
Carpal Tunnel
Reged: 10/21/06
Posts: 2067
Loc: California
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Quote:
Quote:
I did hear a novel use for these things - you can cause streetlights to go off for 10-15 minutes if you manage to zap the daylight sensor.
Is that true??
Because if it is, I am now going to definitely get myself one!
Whoops... Looks like this thread just crossed the red line. I will give this thread a day at the most before it is locked by one of the CN moderators.
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XT10 classic with premium optics
Tri-knob CR2 with compression rings
Round Table Platform
4.5" StarBlast
6" StarBlast6
TV EPs
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Jim Romanski
professor emeritus
Reged: 01/02/05
Posts: 504
Loc: Guilford, Connecticut
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Quote:
I use mine as a finder and its the best pointing device I've ever used.
There's a much publicized case of the guy in NJ that shined his laser at a plane flying low by Teterboro airport. I do not believe that you can even see the beam at normal cruising altitude (not that I plan to test that out nor should anyone). I believe that the FAA has confirmed this as well. In any case, it's a simple matter to avoid using it when a plane goes by that part of the sky.
I think the airplane issue has been over-hyped (the TV show CSI even used a green laser taking down a plane as a plot for a show last season). That said, while this kind of laser won't mess with a planes electronics there is such a thing as a laser that can.
About 35 years ago my Dad worked for a small engineering firm in NJ that did some pioneering work on Lasers. Back then a laser was a large collection of prisms and mirrors and a fairly large device. It took a lot of power to operate one as well.
One day they were outside testing a large pulse laser. A little while later they noticed an FCC truck driving around. They turned on a radio and found that they had jammed the entire dial with noise and realized that the new power supplies they were using were unshielded. Since they were right next to a small airport they must have jammed the entire communications frequency and disurppted all the flights. Ironically this was Teterboro airport!
They shielded their gear and that was the end of it. So I guess technically you can bring a plane down with a Laser. Just not the way you'd think.
I thought you might like this story so I'm quoting myself above from this post a couple years ago: Green Laser Pointer
There are some good links back in that thread too.
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Jim
17.5" Dob "Project"
13.1" Coulter
8” Cave
NP 101 on a CG-5
25x100 binos
Naglers, Ethos, etc.
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Luigi
Carpal Tunnel
Reged: 07/03/07
Posts: 2360
Loc: Massachusetts
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The laser light goes on forever, just like light from distant stars, until all the light is absorbed by something. Looking at the beam the way we do when using it on the sky, the light seen is what's scattered mainly by dust in the air. With no air and dust, you wouldn't see the beam. All laser beams eventually diverge as a consequence of diffraction.
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17.5" f/5 Discovery Truss
IM715 7" f/15 MCT, Eon-120ED
Lunt 60mm Ha on a Nexstar mount.
CG5A coffee grinder, Orion Skyview Alt-AZ
35,19,15 Pans.9 Nag. Meade 24.5 4kSWA, 4.7 5kUWA.
BO-TMB 7mm planetary. Edge-on 3mm.
Zeiss Diascope 85
Zeiss, Leica, Canon IS, Fujinon, Nikon binos
One each generic rescue Greyhound (pictured)
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