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green laser

fredrikb

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JG777

JG777

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Yes they work very well for that. But try and find a very low powered one to reduce the risk of lasering a plane. The problem is you can't always see aircraft that are at high altitudes, typically 5-7 miles and many lasers cover that distance and then some.

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Galilean

Galilean

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I have a 300 mW green laser - it is the business when it comes to aligning your scope and pointing out stars and planets at outreach meetings.

Warning

Please note that 300 mW lasers are potentially dangerous, and are considered unsafe for use in public areas. DO NOT USE THESE!!

There is no reason to use a >5 mW laser for astronomy (reference: http://www.ncbi.nlm....pubmed/20035242). A 5 mW green laser is sufficiently powerful and, importantly, will not cause permanent eye damage (reference: http://hea-www.harva...bolt-6plus.html). Also see here: http://www.universet...laser-pointers/

See post by umadog below

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Alma

Alma

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Suggest you take a look at last Thursday's edition of Fake Britain on iPlayer before buying anything. Most of the prgramme is devoted to green laser pointers and states that most pen type pointers are made from cheap, badly made and unregulated components with labels which are faked to show legal power output to the country they're being exported to, but in fact have totally random power outputs and in many cases are just plain dangerous. Anyone can fake a label.

The progamme also states that 1mW is the legal limit in the UK, but I'm not sure that's the full story on legality.

My strong recommendation is to buy a professionally made device such as the Celestron Green Laser Finderscope Kit from a responsible on-shore Astronomy retailer, not some unregulated off-shore, tax haven Web merchant. The Celestron device is 5mW, the maximum ouput allowed in the U.S. where they have much tighter laws on the sale and use of these things.

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ronin

ronin

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1mw is the limit for a presentation, where people are most likely in a room with the user indicating things on a board or screen.

I do not believe that there is any further consideration then that, so when stood outside pointing out stars, constellations, DSO etc the situation is somewhat undefined. Many will quote the US limit but that by definition is US not UK. Then throw in that the US limit is I believe for what can be sold, not what can be used and it gets complicated.

What happen is the US is you buy a 1mw or 5mW GLP, then buy the upgrade set of internals to make it a 50mw or 100mw. This loophole is much used there.

Not even sure how solid the 5mw rule is in the US, CN pulled someones post about 5 months back - someone asked about a 5mw pointer. There one brand there where you can switch the pointer on and it stays on - useful for aiming a scope. Someone then referred the OP to a site selling them. It was pulled because the site refered to also sold >5mw GLP's, the post did not ask or say anything about GLP >5mw at any time. However that means there are GLP's >5mw for sale in the US.

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Alma

Alma

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My understanding is that the 5mW limit on sale and use in the U.S. is the law - anyone of course can by more powerful devices offshore over the Net, but you won't find domestic based retailers selling anything more powerful than the legal limit. That also seems to be the case with UK retailers, by the way - they don't sell consumer devices labelled with higher output than 5mW. For using a pointer in the U.S, you are supposed to apply for a variance permit to operate a "laser light show" for anything more powerful than a Class IIIa (i.e. up to 5mW) device. I'm sure this is widely flouted and people do perform post-sale re-engineering on their pointers, but technically it would appear to be illegal to do so. I think, by the way, both CN and Astromart pull posts mentioning any device over 5mW as a matter of policy and to stay safe from any legal repercussions. I occasionally use a 5mW green laser pointer (at least, that's what the label says!) and to be honest I don't really understand the need for anything more powerful for purely astronomy use.

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umadog

umadog

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There is no reason to use a >5 mW laser for astronomy (reference: http://www.ncbi.nlm.nih.gov/pubmed/20035242). A 5 mW green laser is sufficiently powerful and, importantly, will not cause permanent eye damage (reference: http://hea-www.harvard.edu/~fine/opinions/z-bolt-6plus.html). Also see here: http://www.universetoday.com/101171/a-look-at-the-hazards-of-green-laser-pointers/

A 300 mW laser is crazy. It's unnecessarily powerful for astronomy and can cause permanent eye damage. It's also a risk to planes should you unexpectedly hit one (this happens). It should be common sense that over-powered lasers shouldn't be used out in the field. It doesn't matter how "careful" you are: almost by definition accidents happen when the unexpected occurs. I get laser-flashed on occasion at outreach events (it's very annoying) and so I know from experience that this occurs despite what people say about their safety habbits. Nonetheless, I'd far rather be flashed with a 5 mW laser than a 300 mW laser.

Sorry, rant over.

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skywatcher250

skywatcher250

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funnily enough im looking to get one - it just seems that the 5 wouldnt appear to reach the stars... in some videos ive seen... agree 300 is ridiculously over the top ! ive heard of people getting in trouble over lasering a plane how on earth would someone know which door to knock on

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umadog

umadog

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Well, according to the link I found above (and what they sell in the astro stores) a 5 mW is sufficient. Remember that this is a laser, not a light bulb, so the wattage rating means a totally different thing. A 60 W bulb is one that draws 60 W of power. If it's an incandescent bulb, most of this power is converted to heat. The rest is converted to light and distributed in all directions. With a laser, the rated power refers to the reading a power meter would provide if you were to point the beam at it. All of this power is concentrated in a very small area, so the brightness (photons per sq mm) is very high. So don't be fooled by laser power ratings. We have a 1.5 W pulsed laser at work and I treat it with the respect accorded to a grumpy elephant.

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Spikey

Spikey

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funnily enough im looking to get one - it just seems that the 5 wouldnt appear to reach the stars... in some videos ive seen... agree 300 is ridiculously over the top ! ive heard of people getting in trouble over lasering a plane how on earth would someone know which door to knock on

It wouldn't take a great deal of effort to triangulate an offender down to a few feet but it would depend on the technology on offer in the aircraft. Let's not forget that waving around a laser beam at night is a pretty good indicator of where it originated and from the point of view of an aircraft it's easy to spot where the beam came from.

My advice - point with your finger ! :)

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michael.h.f.wilkinson

michael.h.f.wilkinson

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but can you take it off and heat your cooling coffee with it !

only joking - back to the subject of lasers, the 1 which FLO sell... the attachable and detachable one - http://www.firstligh...inderscope.html

is this good ?

I do not drink coffee, so no worries there :D. An added bonus is that I can star hop easily on mag 8-9 stars.

My preferred beverage is a tot of whisky (single malt for preference) at the end of the session.

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umadog

umadog

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It wouldn't take a great deal of effort to triangulate an offender down to a few feet but it would depend on the technology on offer in the aircraft

Nope it doesn't take a lot of effort. Here's one idiot who didn't realise that:

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JG777

JG777

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If you are anywhere near an aerodrome ( UK ) particularly within the notification zone ( 10 miles ) you may want to read this http://www.caa.co.uk/docs/33/CAP736.pdf covers use of lasers, balloons and fireworks. Commercial jets are able to pinpoint Lat/Lon very accurately, and I would imagine most general aviation now carries GPS which can do the same thing.

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umadog

umadog

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wow ! def leave that alone then - btw umadog i love how you have a link to everything :) very informative

Thank you.

My girlfriend complains that I have an answer for everything. Presumably this is what you have hit upon. If I give you her phone number could you please explain to her that this presumed flaw is, in fact, useful?

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