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

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

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

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

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

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

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

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

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

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