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Laser pointers again

iancandler

By iancandler
in The Astro Lounge

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steppenwolf

steppenwolf

Posted
Posted

Typical silly government knee jerk reaction!

Last month an Ipswich teenager received a 20-week prison sentence, suspended for 18 months, for using a green laser pointer to dazzle the pilot of a police helicopter.

A better course of action would have been a real prison sentence to send out the right vibes about what is acceptable behaviour and what is not... My green laser made the recent visit to my Observatory of an 8 year old astronomy enthusiast all the more memorable for him a blanket ban on these tools is just daft!

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FLO

FLO

Posted
Posted

My understanding, which might now be out of date, is that it is illegal for someone to 'sell' green lasers with power greater than 5mw. Also, when selling lasers 5mw or less the retailer must establish that the user has a legitimate reason for owning one.

Please feel free to correct me :D

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iancandler

iancandler

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From what I can gather on the net steve the majority of 5mw lasers reaching our shores dont meet the beam dispersal requirements to be classified as a 3A device and thus fall under 3B or 3R which are prohibited from sale to the public.

The general rule of thumb that trading standards seem to be enforcing now is that 1 mw is fine for the general public, up to 5mw where it meets the beam dispersal requirements for those who can prove a legitimate need/use. Though they do state that meeting the beam dispersal requirements renders them not suitable for the purpose of pointing due to the wide beam width/size of the projected dot.

The HPA Radiation Protection Divison has examined many laser pointers available to the general public in order to assess their laser Class and have found a significant proportion of these products to be Class 3R lasers and several Class 3B. The body's natural aversion responses are unlikely to provide adequate protection from eye injury for Class 3B laser pointers.
To satisfy the irradiance criteria, a laser pointer with an output power greater than 1 mW would have to produce an expanded beam to reduce the irradiance below 25 W m -2. As the characteristic feature of a laser pointer is the small spot produced by the narrow beam, expanding the beam area to satisfy the irradiance criteria effectively destroys this useful property. It was therefore extremely unlikely that a laser pointer with a power output in excess of 1 mW would satisfy the Class 3A AEL criterion. Therefore, in general, laser pointers were either Class 1, Class 2 or Class 3B products. The former Class 3B laser pointers, which did not exceed 5 mW, are now Class 3R.

Though we arent breaking the law if we own one, those selling them could well be, and it would be IMHO sensible to check with local trading standards on the exact legislation and how to stay within it.

I can honestly see astronomers getting nabbed by the police for missuse/endagerment if they live anywhere near a flight path, in my experience it takes very little for them to jump in to situations and interpret the law as they see fit, especially when media miss-informed joe public starts ringing their phones off the hook

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661-pete

661-pete

Posted
Posted

Just to clear up one point: I have never used, nor seen being used, any laser pointer for any astronomical purpose (apart from the collimator tool I referred to above). Maybe it's because I have yet to attend my first 'official' star party (I really should get out more... :D). So my question is: do they really help? More to the point: do they help in really clear air conditions when the beam must surely be all but invisible?

My technique over the years has been the time-honoured one: to stand close behind someone, extend my arm past their ear, and utter the words "now can you see what I'm pointing at?"...

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stefski

stefski

Posted
Posted

Hi Pete,

I've seen one used and they are a great teaching tool......Being in the profession I was considering getting one but it now seems I may not be able to. I also live spitting distance from Luton Airport so if I use it, I may get the SAS dropping by :D .

stef

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EA2007

EA2007

Posted
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GLP's are far more direct than using an arm, you will notice the 'small parallax' effect when stood behind someone who has their arm extended as you are never really looking at exactly what they are. As the laser pointer provides a beam probably 100 times as long then any observer in the near area can see exact;y where it is pointing.

With regards to how well they show up against the dark night sky, well it comes down to power really, I had a 1/5mW GLP and it showed up okay on fresh batteries and brilliantly in more foggy conditions but someone on my uni course had a 15mW GLP and that was like looking at a lightsaber beam (albeit a little thinner) it was that bright and it shone a lot further than mine.

Even if the sky appears crispy cold you will be suprsed by the amount of particles there which can reflect the laser beam.

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themos

themos

Posted
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I have one now and my main worry is how to make sure the kids never find it. I'll keep it under lock and key. It says it's a class IIIb, rated at less than 240mW but who knows really? There are no indications of any standards body having checked it out.

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EA2007

EA2007

Posted
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Mine was the same...got it off eBay 2 years ago (its in the bin now, little fella broke, but getting a new one) and it came with no certificate or anything, probably straight in from China where they modify them from 1mW to upwards of 50mW's.

They are cool to use but as has been said in the wrong hands then they will be mis-used. I know this from personal experience as theres some kids the next street up from me who have been shining one around during dusk hours....shame really. We also had an issue at my secondary school about 10 years ago with people bringing in red laser pointers, had one shone in my eyes for a brief second...not a paricularly nice thing to happen.

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661-pete

661-pete

Posted
Posted

Sorry, although I can see how 'convenient' a teaching aid they can be, I don't see the benefits outweighing the risks and disadvantages. Moreover the last thing that amateur astronomers - however responsible and well disciplined (and surely astronomy is one of the most environmentally-friendly of hobbies!) - want, is to be branded in the tabloids as irresponsible and anti-social louts. I'm sure everyone on here who's used a laser has done so carefully and sensibly, but that won't stop the screaming headline "AMATEUR ASTRONOMER COULD BRING DOWN YOUR AIRCRAFT"...

See also the PSP rules...

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PhillyDee

PhillyDee

Posted
Posted

Not allowed at any star parties as far as I am aware. But for a small group, or in your back garden, they are an invaluable tool for people (like me :D) who havent a clue where or what they are doing. As usual, the press go mental over something which the tiniest minority of the population do and want to ban everything. As usual.

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Milliways

Milliways

Posted
Posted

Oh no!! I have a 5mw green laser!

I dont think it should be illegal just should have an age restriction on buying one, it wont be an issue if one is used responsilbly. I use mine because it is so handy, I was asked by my brother in law (who is 10) where some interesting things are, I pointed out the andromeda galaxy, where mars was, M42 nebula and others.. now he is hooked like me! I think the laser is a wonderful tool that i will continue to use :D

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