neufer wrote: ↑Thu Feb 11, 2021 8:04 pm Each laser delivers 22 watts of power — about 4000 times the maximum allowed for a laser pointer — in a beam with a diameter of 30 centimetres.
22 watts of eye sensitive yellow light (= 15,000lumens) shouldn't be sneezed at.
(And it is not clear to me that the ground atmospheric sodium is entirely negligible.)
Chris Peterson wrote: ↑Thu Feb 11, 2021 8:08 pm
"22 watts" is meaningless without considering the density. Every square meter of ground is receiving around 1000 watts in the middle of the day. So what?
A beam with a diameter of
30 centimetres = .0707 m2
So 311 watts per square meter
in the middle of the night.
Re: APOD: Firing Lasers to Tame the Sky (2021 Feb 10)
neufer wrote: ↑Thu Feb 11, 2021 8:04 pm Each laser delivers 22 watts of power — about 4000 times the maximum allowed for a laser pointer — in a beam with a diameter of 30 centimetres.
22 watts of eye sensitive yellow light (= 15,000lumens) shouldn't be sneezed at.
(And it is not clear to me that the ground atmospheric sodium is entirely negligible.)
Chris Peterson wrote: ↑Thu Feb 11, 2021 8:08 pm
"22 watts" is meaningless without considering the density. Every square meter of ground is receiving around 1000 watts in the middle of the day. So what?
A beam with a diameter of
30 centimetres = .0707 m2
So 311 watts per square meter
in the middle of the night.
Yes. So what? Why is that any health or safety concern? You'd be far worse off encountering a 20 mW laser beam of typical 1 mm diameter!
Re: APOD: Firing Lasers to Tame the Sky (2021 Feb 10)
Posted: Fri Feb 12, 2021 2:13 am
by neufer
Chris Peterson wrote: ↑Thu Feb 11, 2021 10:39 pm
Yes. So what? Why is that any health or safety concern? You'd be far worse off encountering a 20 mW laser beam of typical 1 mm diameter!
This long thread has NOTHING to do with any health or safety concern
JohnD wrote: ↑Thu Feb 11, 2021 6:09 pm
Now, please explain why they are visible? So very visible!
The beam from a milliwatt hand held pointer is invisible, unless in a smoke filled room.
Re: APOD: Firing Lasers to Tame the Sky (2021 Feb 10)
Chris Peterson wrote: ↑Thu Feb 11, 2021 10:39 pm
Yes. So what? Why is that any health or safety concern? You'd be far worse off encountering a 20 mW laser beam of typical 1 mm diameter!
This long thread has NOTHING to do with any health or safety concern :!:
JohnD wrote: ↑Thu Feb 11, 2021 6:09 pm
Now, please explain why they are visible? So very visible!
The beam from a milliwatt hand held pointer is invisible, unless in a smoke filled room.
Well, as this whole long thread STARTED with questions about safety, perhaps you can understand the confusion.
Re: APOD: Firing Lasers to Tame the Sky (2021 Feb 10)
Posted: Fri Feb 12, 2021 2:46 pm
by neufer
Chris Peterson wrote: ↑Fri Feb 12, 2021 4:57 am
Well, as this whole long thread STARTED with questions about safety,
perhaps you can understand the confusion.
No mind.
When I'm not doing pratfalls for cheap laughs
I'm mostly trying to educate myself by arguing a case.
I found this one was very ilLUMENating
Re: APOD: Firing Lasers to Tame the Sky (2021 Feb 10)
Posted: Fri Feb 12, 2021 5:23 pm
by JohnD
Neufer,
I was concerned, and matbe started this thread down this route, but Chris' answers have reassured me!
Chris, I'm sorry if my concern - idle, because I'm on the other side of the planet! - gave you a hard time. Thanks again for your patient education!
John
Re: APOD: Firing Lasers to Tame the Sky (2021 Feb 10)
Posted: Fri Feb 12, 2021 5:33 pm
by Chris Peterson
JohnD wrote: ↑Fri Feb 12, 2021 5:23 pm
Neufer,
I was concerned, and matbe started this thread down this route, but Chris' answers have reassured me!
Chris, I'm sorry if my concern - idle, because I'm on the other side of the planet! - gave you a hard time. Thanks again for your patient education!
John
It was a reasonable question. Anybody who has worked around lasers at all knows that a 22 W laser is dangerous. But we're not usually accustomed to encountering them in the form of 30 cm diameter beams. That can distort our intuition.
Re: APOD: Firing Lasers to Tame the Sky (2021 Feb 10)
JohnD wrote: ↑Fri Feb 12, 2021 5:23 pm
Chris, I'm sorry if my concern - idle, because I'm on the other side of the planet! - gave you a hard time. Thanks again for your patient education!
It was a reasonable question. Anybody who has worked around lasers at all knows that a 22 W laser is dangerous. But we're not usually accustomed to encountering them in the form of 30 cm diameter beams. That can distort our intuition.
Re: APOD: Firing Lasers to Tame the Sky (2021 Feb 10)
Posted: Wed Feb 17, 2021 5:30 pm
by JohnD
I am now reassured that the people who use the lasers at Paranal, do so responsibly.
However there may be others who do not. I just came across this video. Do NOT try this at home! https://youtu.be/WAI7Lu4UFi4
Re: APOD: Firing Lasers to Tame the Sky (2021 Feb 10)
Posted: Wed Feb 17, 2021 7:12 pm
by NGC3314
Sites with visible-light AO systems use human plane spotters to avoid accidentally flashing a pilot's vision, with some work in progress on automated systems to first augment, and eventually replace, the spotters. (I am told that UV lasers such as the Robo-AO setup do not need this step). And at least for US systems, there is also a requirement for coordination with (IIRC) NORAD to avoid illuminating sensitive satellites. It is widely believed that NORAD will occasionally insert a fake satellite-avoidance zone to avoid advertising the orbits of satellites they want to protect, but it's not like amateur observers worldwide don't do a good job of tracking most of their orbits anyway.
Re: APOD: Firing Lasers to Tame the Sky (2021 Feb 10)
Sites with visible-light AO systems use human plane spotters to avoid accidentally flashing a pilot's vision, with some work in progress on automated systems to first augment, and eventually replace, the spotters.
Best for all involved that planes avoid any observatories in the Andes.
Re: APOD: Firing Lasers to Tame the Sky (2021 Feb 10)
Posted: Sun Feb 21, 2021 11:08 am
by JohnD
Just for comparison, I read that the US Army is developing a TUPLARP, Tactical Ultrashort Pulsed Laser for Army Platforms, that will deliver fentosecond pulses in the Terawatt range! The average power will be only 20-50 Watts, but in such short pulses will vaporise the target. If it hits it.
See: https://www.sbir.gov/node/1654485
Re: APOD: Firing Lasers to Tame the Sky (2021 Feb 10)
Posted: Sun Feb 21, 2021 2:19 pm
by Chris Peterson
JohnD wrote: ↑Sun Feb 21, 2021 11:08 am
Just for comparison, I read that the US Army is developing a TUPLARP, Tactical Ultrashort Pulsed Laser for Army Platforms, that will deliver fentosecond pulses in the Terawatt range! The average power will be only 20-50 Watts, but in such short pulses will vaporise the target. If it hits it.
See: https://www.sbir.gov/node/1654485
The ability to do damage largely comes down to energy density.
