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



Laser Pointer Store

Would you be able to see a laser beam in space?


Mo13

New member
Joined
Oct 26, 2009
Messages
186
Likes
5
Points
0
I read that someone was able to see laser light reflected by the retroreflectors on the moon with only their eyes during a new moon.

The laser was a 30W green.
That's a lie (If Mythbusters can be trusted). I was watching an episode today where they were testing the moon landing conspiracies. In the end, they went to a lab where scientists use a 1 terraWatt (Maybe it was Gigawatt, either way it was unbelievably high powered) laser and shine it directly onto the retro-reflectors to prove that man was actually there.

Out of something like 200Billion-Zillion (Some ridiculously large number I can't exactly remember) Photons sent out in each pulse, only 2 or 3 returned to their sensors from each pulse. Even if the 30W laser could reach the reflectors on the moon, I find it impossible to believe that and photons would return, let alone enough to perceive with the naked eye.

Again, this is all knowledge I gained on my couch just about 2 hours ago, so don't take it as final word.



EDIT: Here's the video: Moon Myth BUSTED! Moon Laser! - YouTube

It was a 1 Gigawatt laser at the Apache Point Observatory. There are 200 Quadrillion photons fired per pulse, and only 1-3 make it back from each.
 
Last edited:

DrSid

New member
Joined
Jul 17, 2010
Messages
1,516
Likes
59
Points
0
Well you can't really compare .. 1GW puls .. but how long ? 1GW for 1 nanosecond .. is the same as 1W continuous. It could be computed from the photon count, if we knew wavelength .. there is green visible in the video .. but can green be pulsed at such powers ? Not sure ..
Unless we know exactly what laser was used in that 'visual' test, we can't rule it out.
 

Mo13

New member
Joined
Oct 26, 2009
Messages
186
Likes
5
Points
0
Well you can't really compare .. 1GW puls .. but how long ? 1GW for 1 nanosecond .. is the same as 1W continuous. It could be computed from the photon count, if we knew wavelength .. there is green visible in the video .. but can green be pulsed at such powers ? Not sure ..
Unless we know exactly what laser was used in that 'visual' test, we can't rule it out.
That's interesting. I didn't realize how much pulsing vs continuous affected the scenario.
 

HIMNL9

New member
Joined
May 26, 2009
Messages
5,416
Likes
193
Points
0
From the other side (of the problem, not of the moon :p :D) ..... can be interesting if someone with a CW laser of, say, 5 or 10 W (or a working Laserscope, maybe ?), can locate the reflector position, and shoot on it a CW beam at full power, in a clear night (better when the moon is almost totally dark, so reflected light don't interfer too much) ..... if after approximatively 3 seconds you can see some green from a specific point through a telescope, then the test can be considered a success, huh ? ;)

(the only problem can be to find the laser ..... not all the hobbysts can buy similar things :p)
 

DrSid

New member
Joined
Jul 17, 2010
Messages
1,516
Likes
59
Points
0
You also need the laser to be sent through telescope. So it's even more complicated.
 

HIMNL9

New member
Joined
May 26, 2009
Messages
5,416
Likes
193
Points
0
I'm just wondering if an old "catadrioptic" objective can be enough, as beam expander ..... something like the old 800mm Nikon one ..... it work as a reflection telescope, after all :p

I think i still have one somewhere, must made some tests, if i can made an adapter for a pointer, and overall if i find where the damn thing is hidden actually.
 

DrSid

New member
Joined
Jul 17, 2010
Messages
1,516
Likes
59
Points
0
It's all about aperture. Your 800mm Nikon will have how much ? 100mm aperture ? Probably less. I did fine with my russion (brand unknown) 85mmx500mm .. but with astronomic scopes we are talking about meters of aperture.
 

HIMNL9

New member
Joined
May 26, 2009
Messages
5,416
Likes
193
Points
0
^ for observation, yes ..... i was wondering about use it as beam expander ..... can be what ? ..... 80X ? ..... 100X ? ..... not enough for astronomical illumination :p, but must not be so bad, for low divergences.

Just not exactly pocket-size, i have to admit this :p :D
 
Last edited:




Top