Laser Pointers in cold weather

[Dobman (Simon)]

Hi everyone, Ive just recently got a 10mw laser pointer from Bintel & while I was using it as a hand held pointer to show people the night sky it worked perfectly, but as soon as i mounted it on to my scope and used it in cold (below about 9deg C) weather I could barely see it if at all.
I had to resort to a hair dryer to warm it up every 5 minutes.
I had heard that lasers can be affected by the cold but another observers 5mw worked perfectly all night without a hint of it being affected.
Is this common? or do i have a dud pointer?
If its just how they are does anyone have any ideas on making a pointer heater? maybe like a dew heater ?
Any suggestions would be appreciated
Simon

[JohnH]

I do not think it is the laser that is the problem, rather it is battaries that do not like the cold. What kind of batteries do you have installed? Also I believe these gadgets are not intended for continuous use so they may get dimmer if left on for >30s.

[astronut (John)]

Simon & John,
I've just bought a 20mw laser + a mounting device for the scope. If I hand hold the laser, in cold conditions it holds it's strong beam for a long time (1 min) but if I mount it on the scope, the lower section of my 12"LB and it's left off for a few minutes the beam is very weak and does not get any brighter.
Now I know batteries don't like cold conditions, but the instructions on the laser says " does not work well under 15C "
I'm thinking of insulating the laser or heating the tube.
I'll let you know how it works

[bojan]

It is not a problem with batteries, it is a laser diode itself. Because the laser diode output is VERY dependent on die temperature, usually the power supply circuitry (driver) has to cope with temperature compensation as well.
Unfortunately, majority of stuff on the market is of cheap design and lousy quality, manufactured in somebody's garage, no quality control whatsoever... and then sold at premium price to the rest of the world.
In your case, I would recommend keeping the laser in your pocket before use, and then placing it in insulating (plastic ? ) holder/mount on the telescope. If you need to heat something, it is the laser itself, not the tube of the telescope...

[Ingo]

Yes it is the diode itself. Diodes will move up and down in nanometers when too cold or too warm. The crystals inside the green laser are dependent on the IR light the laser is giving off. If the laser isn't exactly putting out 808nm and it's putting out say 807.7mm because it's cold out, you won't get full efficiency of the Nd:YVO4 and KTP Crystals which require 808nm and 1064nm.

If the Nd:YVO4 crystal isn't getting 808nm, then the KTP isn't getting the 1064nm to double the light to 532nm visible green. Hence, efficiency is lost and why your green laser dims.

DPSS lasers will fluctuate for this reason also.

I also wouldn't heat the tube because diodes will die very fast from small things including too much heat or static. Wrapping it in something would be okay, but you'd have to make sure the diode doesn't get too hot, or keep a steady 100 seconds on 10 seconds off duty cycle. If you have a little pen type pointer with no heatsink, it's recommended you keep the duty cycle in mind anyways.

[Starkler (Geoff)]

I find mine behaves itself kept in my back pocket which is fine for handheld use.

[Moonman (Michael)]

Hi Simon

I think Andrews are advertising a unit for $49 dollars that looks very similar to Ian's. Could be worth a look b4 we invest in dew heaters etc.

[davidpretorius]

my "laser" does not like th cold it all....it tends to shrivel!