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Flash Blinded By Green Laser
I've been watching the news channel reports today on green lasers and the
dangers to pilots. I've also been reading the messages here about using green lasers to easily point out objects in the night sky. I don't own a green laser pointer but I have a unique opinion of green lasers because I was flash blinded by one accidentally turned on by Howie Glatter at a star party. When a pilot says he was "flash blinded" by a green laser, I know what he experienced and the disorientation that results. I have also been a very active dark sky advocate for many years and I feel that astronomers should strongly discourage their use for the following reasons: They are a safety hazard and unsafe to dark adapted eyes. They are another form of light pollution. Their use is unnecessary. My initial report of the eye injury follows: begin 9/15/04 message Thanks to all that have contacted me to express their concern about my vision after being hit in the eye by a green laser at the Black Forest Star Party. I cut my vacation at Cherry Springs short and returned home to have my eye checked by my eye doctor. I am hopeful that vision in my eye will return to normal and the problems I am experiencing will subside. The accident happened on Saturday night, just before 8:00 pm as we were making final preparations of our telescopes for a night of clear skies. Me and Tom Ludwig were being shown images taken by a fellow GHHAS member, Tom Bash, on his laptop. I was startled by a bright white flash that blinded my left eye. My eye was saturated by an intense white light and my reaction was to look in the direction I had been facing to see the source of the light. I squinted with my right eye and I was able to see a DNCR truck passing nearby and wondered if it had a white strobe light. I noticed more flashes of white light in the direction of the truck and then flashes of green light. This was followed by green streaks on us, our equipment and the ground where we were standing. We heard a female voice, which was Howie Glatter's wife shouting: "Howie..turn it off", over and over until Howie got control of the laser. I ran to my van to check my eye in my outside rear view mirror. I rubbed my eye hoping that vision would return to normal. I looked up and keeping my right eye closed, blinked my left eye and noticed a dark area in the center of my vision. I closed my left eye, blinked my right eye and noticed a similar dark area but not as prominent. I was very upset by the experience and let Howie know how I felt. Green Laser pointers are not allowed by Cherry Springs State Park; from its Astronomy Field Rules publication: "NO green laser pointers are permitted at any time." The star party organizers, Central Pennsylvania Observers, list four star party rules at the top of the registration packet that all star partiers are provided which includes: "No Green Laser Pointers! The use of green laser pointers on the observing field is prohibited." The Black Forest Star Party web site lists three star party rules and Rule #2 is: " NO GREEN LASER POINTERS (GLPS). GLPs pose a serious danger to eyesight, as well as astrophotography. Please refrain from using these devices while at the Star Party. Anyone caught using a GLP will be asked to leave." I reported the incident to the CPO and park management and an incident report was filed. Howie has expressed his concern to me about what has happened and has offered to compensate me for expenses incurred. I understand that the accident was not intentional but I believe it was completely avoidable by adherence to Star Party and State Park rules. This is my plea to all green laser pointer owners: Don't bring green lasers to star parties. God's gift of eyesight is too precious to be lost in an instant of negligence. Dark skies, Gary Honis, P.E. end message Gary Honis, P.E. Assitant Director - GHAAS Member - IDA Member - POLC |
#2
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On Fri, 31 Dec 2004 04:17:33 GMT, Gary Honis wrote:
I've been watching the news channel reports today on green lasers and the dangers to pilots. I've also been reading the messages here about using green lasers to easily point out objects in the night sky. I don't own a green laser pointer but I have a unique opinion of green lasers because I was flash blinded by one accidentally turned on by Howie Glatter at a star party. When a pilot says he was "flash blinded" by a green laser, I know what he experienced and the disorientation that results. No you don't. The pilot of an aircraft will likely be miles from the laser. The beam will diverge greatly at that distance. Equating that (if that's what it was) with your point-blank experience is ludicrous. Mike Simmons |
#3
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So tell us, what is the safe distance when someone points a green laser
in your face? What, you don't know for sure? Laser beams can be collimated, expanded, even focused (theoretically to a spot 1/4 wavelength in diameter). To make a blanket claim that beam divergence will always protect bystanders shows you have little real understanding of atmospheric propagation. Mike Simmons wrote: On Fri, 31 Dec 2004 04:17:33 GMT, Gary Honis wrote: I've been watching the news channel reports today on green lasers and the dangers to pilots. I've also been reading the messages here about using green lasers to easily point out objects in the night sky. I don't own a green laser pointer but I have a unique opinion of green lasers because I was flash blinded by one accidentally turned on by Howie Glatter at a star party. When a pilot says he was "flash blinded" by a green laser, I know what he experienced and the disorientation that results. No you don't. The pilot of an aircraft will likely be miles from the laser. The beam will diverge greatly at that distance. Equating that (if that's what it was) with your point-blank experience is ludicrous. Mike Simmons |
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amen.
Gary Honis wrote: I've been watching the news channel reports today on green lasers and the dangers to pilots. I've also been reading the messages here about using green lasers to easily point out objects in the night sky. I don't own a green laser pointer but I have a unique opinion of green lasers because I was flash blinded by one accidentally turned on by Howie Glatter at a star party. When a pilot says he was "flash blinded" by a green laser, I know what he experienced and the disorientation that results. I have also been a very active dark sky advocate for many years and I feel that astronomers should strongly discourage their use for the following reasons: They are a safety hazard and unsafe to dark adapted eyes. They are another form of light pollution. Their use is unnecessary. My initial report of the eye injury follows: begin 9/15/04 message Thanks to all that have contacted me to express their concern about my vision after being hit in the eye by a green laser at the Black Forest Star Party. I cut my vacation at Cherry Springs short and returned home to have my eye checked by my eye doctor. I am hopeful that vision in my eye will return to normal and the problems I am experiencing will subside. The accident happened on Saturday night, just before 8:00 pm as we were making final preparations of our telescopes for a night of clear skies. Me and Tom Ludwig were being shown images taken by a fellow GHHAS member, Tom Bash, on his laptop. I was startled by a bright white flash that blinded my left eye. My eye was saturated by an intense white light and my reaction was to look in the direction I had been facing to see the source of the light. I squinted with my right eye and I was able to see a DNCR truck passing nearby and wondered if it had a white strobe light. I noticed more flashes of white light in the direction of the truck and then flashes of green light. This was followed by green streaks on us, our equipment and the ground where we were standing. We heard a female voice, which was Howie Glatter's wife shouting: "Howie..turn it off", over and over until Howie got control of the laser. I ran to my van to check my eye in my outside rear view mirror. I rubbed my eye hoping that vision would return to normal. I looked up and keeping my right eye closed, blinked my left eye and noticed a dark area in the center of my vision. I closed my left eye, blinked my right eye and noticed a similar dark area but not as prominent. I was very upset by the experience and let Howie know how I felt. Green Laser pointers are not allowed by Cherry Springs State Park; from its Astronomy Field Rules publication: "NO green laser pointers are permitted at any time." The star party organizers, Central Pennsylvania Observers, list four star party rules at the top of the registration packet that all star partiers are provided which includes: "No Green Laser Pointers! The use of green laser pointers on the observing field is prohibited." The Black Forest Star Party web site lists three star party rules and Rule #2 is: " NO GREEN LASER POINTERS (GLPS). GLPs pose a serious danger to eyesight, as well as astrophotography. Please refrain from using these devices while at the Star Party. Anyone caught using a GLP will be asked to leave." I reported the incident to the CPO and park management and an incident report was filed. Howie has expressed his concern to me about what has happened and has offered to compensate me for expenses incurred. I understand that the accident was not intentional but I believe it was completely avoidable by adherence to Star Party and State Park rules. This is my plea to all green laser pointer owners: Don't bring green lasers to star parties. God's gift of eyesight is too precious to be lost in an instant of negligence. Dark skies, Gary Honis, P.E. end message Gary Honis, P.E. Assitant Director - GHAAS Member - IDA Member - POLC |
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Tim Killian wrote:
So tell us, what is the safe distance when someone points a green laser in your face? What, you don't know for sure? Mike need not give a hard lower limit for safe divergence to show the logical flaw in Gary's argument. My common experience is that the beams do diverge significantly even after only 100 meters or so, and while I wouldn't want to stick my eye in the beam path, a few kilometers seems more than enough to ensure safety. But even if there were a laser beam that *could* be kept that tight, one needs to show that the green laser pointers are in fact kept that tight. Experience at tens of meters such as Gary had--as unfortunate as that was--won't extrapolate to thousands of meters. Brian Tung The Astronomy Corner at http://astro.isi.edu/ Unofficial C5+ Home Page at http://astro.isi.edu/c5plus/ The PleiadAtlas Home Page at http://astro.isi.edu/pleiadatlas/ My Own Personal FAQ (SAA) at http://astro.isi.edu/reference/faq.txt |
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And if that broadened beam happens to reflect off of a concave surface
on its way to a bystanders wide open pupil? We take for granted that a 100 mm lens will show us invisible objects in the sky. Put 0.1 mW of green laser light into that aperture (an accident I'm sure) and my "common experience" tells me that it could be rather painful to the viewer. They put warning stickers on lasers because no one can foresee every circumstance of their use. Brian Tung wrote: Tim Killian wrote: So tell us, what is the safe distance when someone points a green laser in your face? What, you don't know for sure? Mike need not give a hard lower limit for safe divergence to show the logical flaw in Gary's argument. My common experience is that the beams do diverge significantly even after only 100 meters or so, and while I wouldn't want to stick my eye in the beam path, a few kilometers seems more than enough to ensure safety. But even if there were a laser beam that *could* be kept that tight, one needs to show that the green laser pointers are in fact kept that tight. Experience at tens of meters such as Gary had--as unfortunate as that was--won't extrapolate to thousands of meters. Brian Tung The Astronomy Corner at http://astro.isi.edu/ Unofficial C5+ Home Page at http://astro.isi.edu/c5plus/ The PleiadAtlas Home Page at http://astro.isi.edu/pleiadatlas/ My Own Personal FAQ (SAA) at http://astro.isi.edu/reference/faq.txt |
#7
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In article , Gary Honis wrote:
I've been watching the news channel reports today on green lasers and the dangers to pilots. I've also been reading the messages here about using green lasers to easily point out objects in the night sky. I don't own a green laser pointer but I have a unique opinion of green lasers because I was flash blinded by one accidentally turned on by Howie Glatter at a star party. Do you happen to know the nominal output power of that laser? I have a 5mW green laser, and have tried shining it into my own eye -- briefly (1 second or so) but at short range, so that the beam diameter was smaller than my pupil -- while dark adapted. It's quite annoying, but the effect faded quickly, and I didn't get the feeling I'd done my eye any harm beyond losing dark-adaptation for a while. The overall effect wasn't much more troublesome than looking at a full moon at low magnification, even though of course the beam was much brighter than moonlight. Your report sounds much more alarming than that. I'm wondering whether Howie's laser exceeded 5mW. Stuart Levy |
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In article , Tim Killian wrote:
And if that broadened beam happens to reflect off of a concave surface on its way to a bystanders wide open pupil? We take for granted that a 100 mm lens will show us invisible objects in the sky. Remember that the size of the aperture won't matter much if you shine a narrow collimated beam into it -- a 10mm beam won't put any more light into a 100mm aperture than into a 10mm one, if it's aimed right. I think the question should be (& probably is), if *all* the light from a laser fell into someone's eye and was sharply focused there, what effect would it have? I hope that the 5mW safety threshold was chosen on that basis... Stuart Levy |
#9
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Tim Killian wrote:
And if that broadened beam happens to reflect off of a concave surface on its way to a bystanders wide open pupil? We take for granted that a 100 mm lens will show us invisible objects in the sky. Put 0.1 mW of green laser light into that aperture (an accident I'm sure) and my "common experience" tells me that it could be rather painful to the viewer. On the off chance that you are seriously advancing this as a way that a tight beam could somehow be forced into a pilot's eye at 10,000 m, this optical situation can easily be analyzed. It's improbable in the extreme. I think if you do the math, you'll convince yourself of that, too. If you're talking about the concave surface of a telescope mirror, I of course agree that shining a green laser down a telescope is completely irresponsible. But that's not what we were talking about. We were talking about possibly using green lasers to blind pilots. Look, I think Gary's incident is wholly unfortunate. I wish him the best. But his experience alone says nothing about blinding pilots. If the plausibility of that scenario is to be established, it can't be done by experiences at tens of meters, and it certainly can't be done by positing that the beam just "happens to reflect off a concave surface." Where is this concave surface, exactly? In the cockpit? I'd have an easier time believing that a hawk snatched the green laser pointer up in its beak and shined it in the pilot's eye. For what it's worth, typical divergence for a GLP is 1 milliradian. That is 1 mm of divergence per meter of traversal. By the time the beam has travelled even a kilometer, it has diverged 1 meter. Since your pupil is at most 1/140 as wide, the intensity entering your eye is at worst 140^2 or 20,000 times smaller than it is point blank. You might as well be shining a 250 nanowatt laser directly into your eye. At 10 km (a typical cruising altitude), the intensity is down a further factor of 100. That is 2.5 nanowatts. When you consider that a pilot rarely looks straight down from 10 km, the power probably drops down to something in the neighborhood of 1 nanowatt. Of course, for all I know, someone has concocted a super-GLP that has zero practical divergence. But the ball is in someone else's court now to demonstrate that's actually happened. Brian Tung The Astronomy Corner at http://astro.isi.edu/ Unofficial C5+ Home Page at http://astro.isi.edu/c5plus/ The PleiadAtlas Home Page at http://astro.isi.edu/pleiadatlas/ My Own Personal FAQ (SAA) at http://astro.isi.edu/reference/faq.txt |
#10
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Good question. Any device that can cause such an effect should be banned
from general use. I don't care how helpful they are at star parties etc etc. In Gary's case, I would imagine too that the handheld/randomly direct laser at (I guess) several meters distance would very likey have caused a very short contact with his eye (millseconds rather than seconds). What are the real risks? Why was Stuart's experience (with ~1 second exposure) so much less harmful? (That's a bold test on your part Stuart!) Mark "Stuart Levy" wrote in message .. . Do you happen to know the nominal output power of that laser? I have a 5mW green laser, and have tried shining it into my own eye -- briefly (1 second or so) but at short range, so that the beam diameter was smaller than my pupil -- while dark adapted. It's quite annoying, but the effect faded quickly, and I didn't get the feeling I'd done my eye any harm beyond losing dark-adaptation for a while. The overall effect wasn't much more troublesome than looking at a full moon at low magnification, even though of course the beam was much brighter than moonlight. Your report sounds much more alarming than that. I'm wondering whether Howie's laser exceeded 5mW. Stuart Levy |
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