Green Laser

[mfrymus 5]

My old green laser is pretty much dead.

Its a bad one anyways. Button is getting busted. And it only runs on two AAA batteries.

Looking for something powerful for astronomy.

Looking for one around $75-100

Flashlight style

I see a lot of green lasers from 50-230mW 532nm

But Im not sure what the pros and cons of each are.

I want something bright, will reach far, and is a crisp beam.

[Dave In Vermont 4,951]

In the USA, the standard legal limit is 5mW. Usually more like 3Mw. May I ask what the heck you want a 50+mW laser for? That would have a range of 40+ miles! Mess up some low-orbittal satellites?

Dave

[michael.h.f.wilkinson 20,758]

Lasers as powerful as the ones you mention are potentially very dangerous, and therefore illegal.

[cjdawson 866]

Stick with 5mW, but don't get a cheap one off e-bay or anything like that.

You want one that really is 5mW and not lower.

Don't bother getting one that is over the 5mW for the reasons that others have already said - they're dangerous, not to you, but to anyone that happens to get in the path.

There is another question about lazers.  Why bother having one at all?  The only reason that I know for having one is to be able to point out objects to other people, in a group setting.

Even then, they're limited, so if possible, can you find another way?

btw, I have a mount on my scope for a lazer pointer, but I've not used a lazer in there for several years.  I'm thinking about replacing it with a red-dot, or a talrad.

[mfrymus 5]

I did mean to write from 5mw. Not 50.

But, I guess something between 5 & 50mw sounds good. Something that will be bright with a nice clean green beam.

Is a focusing one recommended?

And how am I supposed to know which one produces a true 5mw or 50mw beam?

The site that I'm looking at doesn't say much about them.

[Thalestris24 3,776]

I did mean to write from 5mw. Not 50.

But, I guess something between 5 & 50mw sounds good. Something that will be bright with a nice clean green beam.

Is a focusing one recommended?

And how am I supposed to know which one produces a true 5mw or 50mw beam?

The site that I'm looking at doesn't say much about them.

5mW is potentially dangerous and 50mW would definitely be very dangerous!

Louise

[Jim Steele 255]

I would have severe resevations about getting anything above 5mW; purely from a safety point of view but there is very little legislation on what you can buy in the UK.

The should all be compliant with the current British Standard, BS EN 60825-1:2014. but many laser pointers available to the general public have been assessed by the HSE and found that a significant proportion of these products are incorrectly classified and often dangerous. The natural aversion responses are unlikely to provide adequate protection from an eye injury to such laser pointers.

A lot of the imports from China dont have the correct labeleing and as such could be dangerous, if you accidently shine one in your, or someoene elses eye..

1mW is classed as safe providing you dont magnify the light (or focus it), since the eye can be averted long enough not to cause permanent damage. 5mW is usually safe, at 5x the blink reflex limit you may cause injury if you get hit by it

[michaelmorris 2,160]

_{As far as I know there is no actual legal limit on the size of laser you can own.  However, government advioce is that anything over 1mW (Class B laser) can cause harm with prolonged exposure and anything over 5mW (Class 3R laser) should be avoided near people (i severly paraphrase here).  see https://www.gov.uk/government/publications/laser-radiation-safety-advice/laser-radiation-safety-advice}

From my experience, 5mW is plenty powerful enough to point out objects in the night sky to a crown of people. 

[Charic 2,730]

I'm  watching this thread with interest, as I cant see any reason I would want to have a Laser for Astronomy except to hand hold and point at a particular point in the sky, guiding someone else  nearby to look at the same target. For this any low powered pencil or bullet  type laser should work, or even one of the Mag-lites with a fine pencil beam could suffice. 

Its also a dead give away to your location, should you have all your equipment stored outside, if, having a Laser attached to the scope as a form of laser dot finder, could attract undesirables ?

I have to add I did buy a laser light projector  yesterday for indoor use, but for a completely different use,   for small events and parties creating moving and morphing patterns between Stars, Snowflakes, Star-bursts and dots. It also reacts to bass sound so when  jamming on my keyboards, the effects are pretty amazing without needing a lighting engineer. The other issue I have here is with low flying aircraft, it only takes one stray beam to attract and warrant more unneeded attention from the authorities?

Used safely and solely for your intended reason, I hope it works for you, but for now, not my choice. 

Edited October 19, 2015 by Charic

[mcolbert 121]

FWIW the only reason I am looking at lasers at the moment is to experiment with studio photography of miniatures - no astronomical use.

Even then the laser will be attached to a fibre optic cable.

michael

Edited October 19, 2015 by mcolbert

[Psychobilly 7,133]

Looks like changes maybe afoot....

http://www.bbc.co.uk/news/uk-wales-34572168

Having worked with powerful lasers for the last 25 years it's surprising what available to "joe public"  on-line....

Peter....

[Dave In Vermont 4,951]

The article you linked, Peter, is another spreading half-truths in the name of sensationalism. Notable where it states a 5 - 7mW laser can burn your name. They can't. But flashed onto the wind-screen of a plane or car - one could easily cause a disaster. There was an outfit in China that sold green-lasers bragging how they'd light things on fire a few years ago. Don't know if they got stopped or what. And don't bother asking me for their name!

These things can be dangerous in the hands of fools of all ages. Another shining <koff!> example of mankind's technology growing in leaps, while intelligence sits back in the weeds.

Off to play Star Wars,

Dave

[Garethr 276]

FWIW

In my view 99.999% of the users on this forum would only use this for Astro use and are well aware of the dangers of a randomly pointed a laser into the sky.

As someone who lives within 10 miles of Heathrow airport I often use a laser to point out targets in the night sky but am aware of any aircraft in the area around us.

Most issues are caused by deliberately pointing the laser at the aircraft from dead ahead as they approach the runway or up at police helecopters for a reason !!!!

They are a great tool to show people the night sky 

Gareth

Edited October 20, 2015 by Garethr

[cjdawson 866]

I'm almost tempted to say "Hands up those on here that have used a laser to point out things in the night sky?" then "Put your hand down if you scan the sky in the area that you are going to point for planes, etc before turning on the beam"

I'm fairly certain that a few hands will go up, then all of them will come down, except for maybe one sheepish hand, that will be a little embarrassed about not having thought of doing it consciously.

[Thalestris24 3,776]

The article you linked, Peter, is another spreading half-truths in the name of sensationalism. Notable where it states a 5 - 7mW laser can burn your name. They can't. But flashed onto the wind-screen of a plane or car - one could easily cause a disaster. There was an outfit in China that sold green-lasers bragging how they'd light things on fire a few years ago. Don't know if they got stopped or what. And don't bother asking me for their name!

These things can be dangerous in the hands of fools of all ages. Another shining <koff!> example of mankind's technology growing in leaps, while intelligence sits back in the weeds.

Off to play Star Wars,

Dave

It actually says 5 - 7 Watts, not mW

[Dave In Vermont 4,951]

It actually says 5 - 7 Watts, not mW

That dates me. Last I looked, a 5 to 7 Watt laser would be as big as a refrigerator. Perhaps I'll take a stroll and see what malevolent entities have available to them.

Dave

addendum: YIKES!!

Edited October 20, 2015 by Dave In Vermont

[Thalestris24 3,776]

That dates me. Last I looked, a 5 to 7 Watt laser would be as big as a refrigerator. Perhaps I'll take a stroll and see what malevolent entities have available to them.

Dave

addendum: YIKES!!

This is cool - 8 x 5W but very dangerous! https://www.youtube.com/watch?v=iVrJUbeuG44

[Dave In Vermont 4,951]

This is cool - 8 x 5W but very dangerous! https://www.youtube.com/watch?v=iVrJUbeuG44

Me thinks I'll start carrying a mirror.....

Dave the Inflammable

[Thalestris24 3,776]

This has probably strayed a bit from astronomy now... I hope it's put the op off from trying to use any lasers greater than 1mw.

[Psychobilly 7,133]

Yes technology has moved on quite quickly and become a lot cheaper... 

We used to design and manufacture CO2 (up to 100W)  and flash lamp pumped dye and ruby lasers and we used to buy in Laser Diode arrays, YAG's  and the 500W plus CO2 jobs...

I have dug out a couple of my old laser pointers to check on the power meter...

Red 2.5mW   Green 8.2mW

Peter...

[Darryls 3]

mfrmus asked:

"And how am I supposed to know which one produces a true 5mw or 50mw beam?"

I find that if I buy from a site that sells astronomy equipment, I usually will get one that is bright enough for my purposes.  Some sites even state that their lasers are "tested to be 5mw".  For personal pointing (used with your telescope under dark skies) even the cheap ebay ones have worked for me.  But for group pointing, you want a 5mw "tested" one.  If you end up with a dim one, just have the group cuddle up close!

[Andy Mitchell 56]

The green lasers you are likely to buy are actually infrared lasers that shine the beam through a frequency doubler. This converts some of the IR light into green. In theory you should then have a filter to prevent the remaining IR coming out the front. Guess what, lots of the cheap lasers online  (especially eBay) don't and they put out much more IR than visible light. I've heard tales of the optics bending the IR by a different amount so the invisible beam of eye death may not be where the visible green is. Potentially very dangerous if that's true as you wont blink on just IR.

As someone else said the power figures quoted are often not reliable, they may quote the power of the driving IR laser to make it sound better, they may quote the visible power and not filter the IR making the laser look safe when it isn't or they may just make it up.

There is no specific law banning laser pointers over 1mW in the UK, trading standards use general legislation on unsafe goods to pull any they find from sale. You can legally own one. A true 5mW laser pointer is still reasonably safe, you could cause your eyes harm but it generally involves deliberately not blinking and staring into the beam.

Above that, things start to get properly nasty.

[Stu 30,346]

The green lasers you are likely to buy are actually infrared lasers that shine the beam through a frequency doubler. This converts some of the IR light into green. In theory you should then have a filter to prevent the remaining IR coming out the front. Guess what, lots of the cheap lasers online (especially eBay) don't and they put out much more IR than visible light. I've heard tales of the optics bending the IR by a different amount so the invisible beam of eye death may not be where the visible green is. Potentially very dangerous if that's true as you wont blink on just IR.

As someone else said the power figures quoted are often not reliable, they may quote the power of the driving IR laser to make it sound better, they may quote the visible power and not filter the IR making the laser look safe when it isn't or they may just make it up.

There is no specific law banning laser pointers over 1mW in the UK, trading standards use general legislation on unsafe goods to pull any they find from sale. You can legally own one. A true 5mW laser pointer is still reasonably safe, you could cause your eyes harm but it generally involves deliberately not blinking and staring into the beam.

Above that, things start to get properly nasty.

Interesting, thanks Andy

[LukeSkywatcher 15,473]

They dont like the cold. I bought one from an astro retailer a few yrs ago...........just to have one for pointing out things to people. It never quite worked out. Then i tried to use it for playing with my dog...............she couldn't have been less bothered (i think its only cats that chase the beam). Its sat in its box now for yrs unused.

Theres 30 quid i'm never getting back.

[Thalestris24 3,776]

They dont like the cold. I bought one from an astro retailer a few yrs ago...........just to have one for pointing out things to people. It never quite worked out. Then i tried to use it for playing with my dog...............she couldn't have been less bothered (i think its only cats that chase the beam). Its sat in its box now for yrs unused.

Theres 30 quid i'm never getting back.

Lol, they're only a couple of quid on Ebay!