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AXAF
sage
Reged: 09/15/04
Posts: 236
Loc: New England
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I observed last night in the cold (temps in the 30s) with friends and proudly brought along my new green laser pointer. However, when I went to shoot the beam up into the sky, I got barely any sort of output. I surmised that the cold was the cause of the problem, and tried to warm it up by keeping it in a jacket pocket, which seemed to help though not much. Does anyone have a better approach?
As soon as I brought it back home and gave it a chance to warm up, the beam shined brightly again.
-Gary
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Torus Optics 32cm f/6 Dob
Osypowski Equatorial Platform
Fujinon 10x70
Coronado PST plus SolarMax 40 filter
Vixen GPD2 on a Berlebach Tripod
StellarVue SV90T
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nyc_nurse
sage
Reged: 07/29/09
Posts: 254
Loc: nyc
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That's pretty much what happens with the output of lasers in the cold. Some models boast feed-back circuitry that reduces temp related output drops but best thing would be to keep it as close to your body as possible when not using it.
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Sam P.
www.agirlandaguy.blogspot.com
Pentax 7X50
TV-102 APO w/ (Starbeam - on backorder  )
Ash Gibraltar w/ SkyTour DSC
NZ3-6, N9T6, N13T6
TV 20 Plossl
Pan 24, 35
Pentax XW10, XW14
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scott m
sage
Reged: 12/06/07
Posts: 227
Loc: Hatfield Pa
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I keep mine next to a hand warmer in my pocket, it still gets cold rather quickly but keeps it warm enough to make it usable.
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Orion Astroview 120st EQ w/rigel+2"diag(Cosmo)
Zhumell 10 inch dob w/telrad (Oddball)
Nikon AE 10x50 Binos
Astro-Tech Paradigm 5,8,12,15,18,25mm
GSO SuperView 30mm,20mm,15mm,10mm
Knight Owl EWA 6mm,9mm
Zhumell Plossl EP Kit
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Tim A.
professor emeritus
Reged: 09/19/07
Posts: 663
Loc: 40 30'N 105 3'W
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I keep mine in my shirt pocket, next to my skin. Depending on the temperatures, whatever layers are above it seem to keep it warm enough to work at 100%.
By the way ... does permitting a GLP to get very cold (sub-zero F) harm it in any way? I was wondering if it's OK to leave it in my vehicle full-time, but it sometimes gets very cold here. I would never use it until I'd warmed it up to about 70 degrees (shirt-pocket temperature), but it would go through some temperature extremes in the "off" state. Does anyone know for sure if that's OK? I've been keeping it indoors.
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Tim -- Colorado
12.5" f/5 Dob (Starbucket)
Celestron CPC800
Celestron CR-150 HD on CG5-GT
Galileoscope
Oberwerk Deluxe II 20x80 & Ultra 10x50
Celestron Regal LX 8x42
Bio-binoculars 1x6
"Me? Crazy? Oh, yeah. Crazy like an ox!"
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Tony Flanders
Post Laureate
Reged: 05/18/06
Posts: 3934
Loc: Cambridge, MA, USA
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Quote:
I tried to warm it up by keeping it in a jacket pocket ...
Laser pointers are nice and slender. I keep mine in my pants pocket, where it stays *really* warm. Jacket pockets are for things that need warmth, but not so much, like eyepieces and eyeglasses.
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Tony Flanders
First and foremost observing love: naked eye.
Second, binoculars.
Last but not least, telescopes.
And I sometimes dabble with cameras.
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dmbryan
member
Reged: 07/01/09
Posts: 30
Loc: Birmingham, Alabama
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Quote:
Quote:
I tried to warm it up by keeping it in a jacket pocket ...
Laser pointers are nice and slender. I keep mine in my pants pocket, where it stays *really* warm. Jacket pockets are for things that need warmth, but not so much, like eyepieces and eyeglasses.
Mine stays in my pant pocket as well.
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Starblast 4.5
CPC 1100
cheap 10x50 binos
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dyslexic nam
super member
Reged: 01/28/08
Posts: 171
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"Is that a Green Laser Pointer in your pocket, or are you just happy to..." ah, nevermind.
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F.Meiresonne
Post Laureate
Reged: 12/22/03
Posts: 3627
Loc: Eeklo,Belgium
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I builded a sort of heater with resistors. Works with a 9 V battery and seems to work in cold temperatures at least to i level i can produce a beam.
I have know a 12v battery but i have not tried it yet.
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Freddy Meiresonne
Obsession 18 inch #1638
Orion Optics 8 inch F/4.5 -1/8 wave optics -Vixen GP-E
22x85 Helios Apollo (=GO SS)
15x70 TS Marine (=Obie Ultra)
10x60 Helios Quantum 4(= Obie Mariner)
10x50,8x40 Helios Nature sport plus
Eyepieces in use :Pan 35,24,19, N13T6, Pentax 10 XW, N9T6, Ultrascopic 7.5, TV2, BGO 12.5 and 9 mm
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Michael A. Earl
vendor- Canadian Satellite Tracking and Orbit Research
Reged: 11/17/08
Posts: 1334
Loc: Brockville, Ontario, Canada
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Something that has not been mentioned in this thread so far is the reason why green laser pointers do not perform well in the cold.
The answer is the batteries, not the laser itself. Unfortunately, most green laser pointers perform best at the nominal voltage (normally 3V). If that voltage is lower by a fraction (which often happens to cold batteries), the laser does not perform at maximum.
I had a laser pointer that used two AAA batteries. After some time, I threw it away. Why? I found that it would cost more in AAA batteries than simply buying a new one with rechargable CR2 batteries. After only several hours use (in normal temperatures), the pointer would need new batteries. This is not "economically viable" and not too nice to the planet, using all those alkaline batteries.
My older pointer could not take rechargeable AAA batteries because they are rated at 1.2V not 1.5V, so the total voltage (2.4V) would be much too low.
I bought a green laser pointer that uses rechargeable CR2 batteries. With several rechargeable CR2 batteries, I can use the first one in the cold (keeping it near my own warmth if required) until it begins to dim, then if necessary, swap the cold battery for the warm. That way, I will never have to buy batteries again (until the rechargeable CR2s wear out that is).
Until someone comes up with a green laser pointer that works with two AAA batteries and performs well anywhere between 2V and 3V, instead at exactly 3V, this is the best solution I have come up with so far.
Unless you live in a warm climate, don't even go near the conventional green laser pointers. They are incredibly wasteful and badly designed in my view.
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Michael A. Earl - Vendor
Canadian Astronomy, Satellite Tracking and Optical Research
www.castor2.ca
Celestron NexStar 11 GPS
Celestron NexStar 8i SE
SBIG ST-9XE CCD
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F.Meiresonne
Post Laureate
Reged: 12/22/03
Posts: 3627
Loc: Eeklo,Belgium
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I believe batteries do come in to play but i was under the impression that a leasar itself will not work well in the cold.
I have a led lamp with a 9V batterie giving me never any problem in the cold.
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Freddy Meiresonne
Obsession 18 inch #1638
Orion Optics 8 inch F/4.5 -1/8 wave optics -Vixen GP-E
22x85 Helios Apollo (=GO SS)
15x70 TS Marine (=Obie Ultra)
10x60 Helios Quantum 4(= Obie Mariner)
10x50,8x40 Helios Nature sport plus
Eyepieces in use :Pan 35,24,19, N13T6, Pentax 10 XW, N9T6, Ultrascopic 7.5, TV2, BGO 12.5 and 9 mm
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Michael A. Earl
vendor- Canadian Satellite Tracking and Orbit Research
Reged: 11/17/08
Posts: 1334
Loc: Brockville, Ontario, Canada
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Quote:
I have a led lamp with a 9V batterie giving me never any problem in the cold.
LEDs take much less power than the green laser diodes do. In fact, LEDs can work with a single 1.5V battery.
I do know what you mean though. I have a red laser pointer that does not mind the cold at all. In fact, it works perfectly in temps below 0.
The green ones, however, are terrible. I tested out the "battery theory" several weeks ago. I left my first green laser pointer out in the 5C temps for a few hours. When I brought it back in, of course it was completely dead. This was not due to the batteries freezing (it was not below 0), but the batteries could no longer hold their nominal voltage of 3V, or they could not handle the current draw in their colder state. Either way, the power was down.
However, with the green laser pointer still cold, I replaced the cold batteries with warm ones. The pointer was completely cured! It blazed brightly once again! This meant that the laser itself was not to blame, but the batteries were.
All batteries I used were completely fresh -- right out of the package. When I let the original batteries warm up, they performed perfectly once again.
Again, I think rechargeable CR2 batteries are the way to go with the green laser pointers.
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Michael A. Earl - Vendor
Canadian Astronomy, Satellite Tracking and Optical Research
www.castor2.ca
Celestron NexStar 11 GPS
Celestron NexStar 8i SE
SBIG ST-9XE CCD
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F.Meiresonne
Post Laureate
Reged: 12/22/03
Posts: 3627
Loc: Eeklo,Belgium
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Green ones are indeed very sensitive.
A blue laser is very insensitive to cold. But very expensive and one does not sees the beam well enough in the dark...
But as said some batteries(types) work better then others
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Freddy Meiresonne
Obsession 18 inch #1638
Orion Optics 8 inch F/4.5 -1/8 wave optics -Vixen GP-E
22x85 Helios Apollo (=GO SS)
15x70 TS Marine (=Obie Ultra)
10x60 Helios Quantum 4(= Obie Mariner)
10x50,8x40 Helios Nature sport plus
Eyepieces in use :Pan 35,24,19, N13T6, Pentax 10 XW, N9T6, Ultrascopic 7.5, TV2, BGO 12.5 and 9 mm
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ischua
Under the Radar
Reged: 07/17/08
Posts: 287
Loc: Below Snow Plop, N Y
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Don't know if this will work some cellphone car chargers put out 3v why not hard wire one to run off a 12v battery
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Mike
Meade 2080
and assorted parts
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Michael A. Earl
vendor- Canadian Satellite Tracking and Orbit Research
Reged: 11/17/08
Posts: 1334
Loc: Brockville, Ontario, Canada
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Quote:
Don't know if this will work some cellphone car chargers put out 3v why not hard wire one to run off a 12v battery
Unless you know exactly what you are doing, I would recommend against it. It is not to protect you, but your laser pointer (and possibly the cell phone charger too).
You would have to know the current draw (amperage) of the laser pointer and the cell phone charger. I did toy with the idea of using a transformer to 3V (or thereabouts), but I opted for the rechargeable battery solution because I would have to carry an inverter wherever I was if I used the transformer solution.
It seems that everything has a price and laser pointers are still too expensive to toy around with. I guess you can say it is like hooking up an external power supply to your iPod Shuffle, not adviseable 
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BGreenstone
member
Reged: 11/20/09
Posts: 70
Loc: Austin, TX
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One thing to keep in mind about the CR2 rechargeables is that they are Lithium, and lithium rechargeable batteries drain instantly when they're cold. Professional photographers all know to keep their camera batteries in their warm pockets before using them in cold weather - otherwise they run dry in minutes rather than hours.
-Brian
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Sarkikos
Carpal Tunnel
Reged: 12/18/07
Posts: 1727
Loc: Suburban Maryland, USA
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If you have the GLP mounted to your telescope, and you have a portable power supply attached to your mount for dew control strips, you can reserve one small strip to wrap around the GLP. That will keep the laser and its battery warm for the night. That is the only sure fire way I have found to maintain a GLP in working order for hours if the temperature drops below about 50 deg F. Nothing else has worked for me. I've even strapped a portable power supply around my grab-n-go 4.5" ball Newt, connected a dew strip and wrapped it around a mounted GLP to locate objects while holding the scope in my arms.
Mike
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C10-NGT on 1stBase (DSO); Z8, Bosma 6" f12 MCT (NSO); 6" f5 Newt, 4.5" f4.4 Ball (Handheld RF w/GLP); C4-R, 130ST (NSO/RF/DS); 90mm f13 MCT (Luna/DS); ST80+Crayford (RF/DS); SkyMaster 25x100/15x70; Zhumell 20x80; Barska XWA 10x50/8x40 (9.5°!); CV 2.3x40 (26°!); BV-125C; CG5, CG4 (2d); SV AZ, 501HDV on 055XB, P+ on Oberwerk; QuikFinder, Telrad; 11x70 RACI Finder; Dynamo Pro, Dew-Not; Orion 5-Filter Wheel; ES 14 100°, Baader Zoom, Baader GO 9mm, Plossls, Orthos, Kellners; Barlows, Reducers
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FLYcrash
sage
Reged: 08/29/09
Posts: 231
Loc: Chicago, IL, USA
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Just a comment about the physics of diode lasers...
Semiconductor devices pass a current that is highly nonlinear in the voltage, nothing like a resistor. If you look at current plotted in terms of voltage, there is a threshold voltage below which there is basically no current and above which the current shoots up. Lasers are nonlinear themselves, too, needing a threshold light intensity in order to lase. And then there is the fact that green laser pointers work by frequency-doubling 1064 nm (infrared) light into 532 nm (green) light with a nonlinear crystal.
The result of all of these nonlinearities is that a very small change in voltage is the difference between a bright beam and no beam (or something like weak, incoherent red light coming out of the lens). My cheap GLP from Hong Kong stopped making a beam in less than an hour of operation, though a fresh pair of alkaline batteries fixed this for now.
Cold itself should not hurt a diode laser unless the temperature change is fast enough to break components via thermal contraction. I know that diode lasers can work at liquid nitrogen temperatures, but dropping one directly into a dewar is probably not advisable.
As already mentioned, the cold lowers the voltage output of batteries enough to make the difference between a beam and no beam, even with fresh batteries.
There are green laser pointers that have voltage-regulating circuitry to keep the beam at a good intensity as the battery discharges (and probably also in the cold...?). They cost a lot more - in the neighborhood of US $100.
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Raman
Young, myopic, non-astigmatic eyes; polycarbonate spectacles; Minox HG 8x33, 10x52 binoculars
Orion XT4.5 (114mm, f/8) Dob
TeleVue 40 Pl; Orion Sirius 25, 10 Pl; Vixen 17 LVW; Pentax 7 XW; Orion Deluxe 2x barlow
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