Green Laser Pointers

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WaveGuide
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Green Laser Pointers

Post by WaveGuide »

Has anyone tried one of those green light laser pointers? I bought one recently and fitted it to my scope with a specially made mount. The idea is to use this as the first coarse pointing device before using the finder scope.
The pen-like pointer produces a superb fine beam of green light. The whole beam is completely visible in the dark and has a range of several kilometres and is quite fascinating. However, after leaving the scope outside in readiness for darkfall, I was a bit miffed to find the laser almost dead when I turned it on. The batteries were new, so I figured it was the temperature. It must have been between 5 - 10 degrees C when I tried it. Allowing the gizmo to warm up indoors returned the power to normal. How come they sell these units as astronomical pointers if they fizzle out in the cold?

WG
barf
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Post by barf »

i use one but not as a scope guide, just a pocket one, use it for pointing things out to others (or you can scare sheep with it)

keep mine in me pocket so it works fine.
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Post by joe »

http://www.popastro.com/phpBB2/viewtopi ... 49&start=0
Also if you do a search in Telescopes and Instruments you will find a few other discussions on the subject of lasers.
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carlos dfc
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Re: Green Laser Pointers

Post by carlos dfc »

WaveGuide wrote:How come they sell these units as astronomical pointers if they fizzle out in the cold?
The main intention is to use them hand-held - hence the press-button switch on most of them, instaed of a switch which will allow you to leave it 'on'

I find if I keep mine in my pocket, it's OK - but on the odd occasion I've left it lying around outside, it does struggle when it gets cold.
Although, if you warm in in your hands fr a minute or so - it will work fine again - and once you get it 'on' the power running through it tends to keepi t warm enough so it doesn't fade out.

edit....they also make a great cat-toy. :D
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WaveGuide
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Re: Green Laser Pointers

Post by WaveGuide »

carlos dfc wrote:The main intention is to use them hand-held
Agreed, but I bought one, plus a proper adjustable mount after seeing them advertised on the Telecsope House website. There are lots of other retailers selling these pointers and mounts for astronomical telescopes. So, if these units are not suitable for use between say 0 - 10 degrees C, they are not really useful for telescope sighting and should not be marketed as such.

I seems from the previous discussions that some form of insulation jacket is the most practical approach to keeping them going. If that doesn't work, my fifteen quid laser mount was a total waste of money. Not impressed.

WG
agentgonzo
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Post by agentgonzo »

I think that it may be a combination of the laser diode and the batteries at low temperatures that are contributing to the fact that they don't work that well in low temperatures. I know that battery voltage drops when you cool them, so this will affect the laser. I just keep mine in my trouser pocket and it's fine. If you want to mount it on a scope and have one of the button press ones, look at a cheap hose clamp or jubilee clip to keep the button depressed when on your scope. That should sort it.

They are great things though. I was on a holiday with my family and using it to point out the stars. they were more interested in the laser than the sky though. :(
martinss
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Post by martinss »

Hi All,

As some of these pointers don't work in the cold, it might be worth wrapping a fabric hand warmer round it...I left a post about how I used one with my camera here:

http://www.popastro.com/phpBB2/viewtopic.php?t=7314

It really did work a treat and might be worth a bahs on those forthcoming cold nights out!!!

Don't look down!

Martin
'I can calculate the motion of heavenly bodies, but not the madness of people...'[/b] Sir Isaac Newton
Scope:LXD75 10" SNT, Laptop, UnModded Phillips SPC900NC, Canon EOS5D and associated bits and bobs; Also using a stolen 2.5" Skywatcher Refractor (my son's).
Websites: http://www.hantsastro.org - http://www.m109.co.uk - http://www.saban.co.uk - http://www.workingimage.co.uk . Wishlist - Moonlight Crayford[/size]
brian livesey
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Post by brian livesey »

A green laser pointer makes a great finder on my 20cm Newtonian. The pointer can be wrapped in a hand-warmer as sold in camping shops to keep it working in low temperatures. Or a heating strip can be used that needs a power supply.
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martinss
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Post by martinss »

We must be on the same wave length here Brian!!
'I can calculate the motion of heavenly bodies, but not the madness of people...'[/b] Sir Isaac Newton
Scope:LXD75 10" SNT, Laptop, UnModded Phillips SPC900NC, Canon EOS5D and associated bits and bobs; Also using a stolen 2.5" Skywatcher Refractor (my son's).
Websites: http://www.hantsastro.org - http://www.m109.co.uk - http://www.saban.co.uk - http://www.workingimage.co.uk . Wishlist - Moonlight Crayford[/size]
brian livesey
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Post by brian livesey »

:wink:
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WaveGuide
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Post by WaveGuide »

Using thermal insulation, electric heaters and chemical hand warmers are all well and good, but it doesn't excuse retailers like Telescope House
selling these laser kits at quite high prices without warning you it will not work at temperatures below 10 degrees C.
See their advert here: http://www.telescopehouse.co.uk/page.as ... =001lngdef

I didn't buy my kit from them, but many other retailers sell the same product with no mention of its limitations for use on astronomical telescopes.

WG
martinss
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Post by martinss »

Hi WG,

That's very true indeed and it is something that retailiers need to be aware of. The information should indeed be put into the product descriptions on their websites. Perhaps you could give them a call and tell them...

There aren't many battery products (especially those that use small batteries) that will work sufficiently well for long periods of time in the cold before becoming useless - (even my camera with it's meaty battery dies a death after a short time in the cold)...so from now on (as per my forum post above) , I'll be wrapping hand warmers around my bits and pieces to keep them warm and working for longer.

Doesn't excuse slight misrepresentation on behalf of retailers though...

ATB,

Martin
'I can calculate the motion of heavenly bodies, but not the madness of people...'[/b] Sir Isaac Newton
Scope:LXD75 10" SNT, Laptop, UnModded Phillips SPC900NC, Canon EOS5D and associated bits and bobs; Also using a stolen 2.5" Skywatcher Refractor (my son's).
Websites: http://www.hantsastro.org - http://www.m109.co.uk - http://www.saban.co.uk - http://www.workingimage.co.uk . Wishlist - Moonlight Crayford[/size]
beamer3.6m
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Post by beamer3.6m »

Maybe a stupid question but are they any better than a red dot finder for a single user, i.e. not needed to point out things to others.

I am looking for a simple addition to my 8" Newt as the finderscope is little help with the first basic alignment.

I could put my red dot finder on it but this involves drilling the tube to fit the bracket.
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martinss
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Post by martinss »

Hey Beamer,

I've stuck my red dot finder onto my usual finder with double sided carpet tape.

It works a treat...

Image

As it is quite a bit higher than the main OTA, I propped the back of it up a bit to make sure I had enough ALT adjustment. Then, I aligned as normal and you're off.

But what about the tape?? Solid as a rock, and easy to gently prise off if you need to - especially if the paint underneath is nice and smooth..

ATB,

Martin
'I can calculate the motion of heavenly bodies, but not the madness of people...'[/b] Sir Isaac Newton
Scope:LXD75 10" SNT, Laptop, UnModded Phillips SPC900NC, Canon EOS5D and associated bits and bobs; Also using a stolen 2.5" Skywatcher Refractor (my son's).
Websites: http://www.hantsastro.org - http://www.m109.co.uk - http://www.saban.co.uk - http://www.workingimage.co.uk . Wishlist - Moonlight Crayford[/size]
nealeh
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Green Laser Pointers

Post by nealeh »

Green Laser Pointers
martinss wrote:There aren't many battery products (especially those that use small batteries) that will work sufficiently well for long periods of time in the cold before becoming useless
I recall being told that rechargeable batteries hold their charge longer if stored in a 'fridge. Might be worth trying those with your laser.
martinss wrote:so from now on (as per my forum post above) , I'll be wrapping hand warmers around my bits and pieces to keep them warm and working
Following the theme of rechargeable, you might find it cheaper to use the saline based warmer products similar to those used to warm wine. They cane be regenerated by submersing in near boiling water for a few minutes. You need to be careful transporting them though to avoid triggering the heating mechanism (a metal 'clicker') by accident.

Can anyone describe how they work? It seems as though they generate heat out of nothing!
Cheers,
--
Neale
Insanity is hereditary, you get it from your children
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