Looking for a 20 mW blue laser pointer

I'm looking for a 20 mW blue laser pointer to use as a pointing tool during astronomy meet-ups, replacing my 532 nm DPSS pointer. I already have laserbtb's '5 mW' 450 nm laser (which is actually 10 mW) but would like to upgrade the power a bit. So far I've only been able to find ridiculously overpowered 447 nm and 473 nm laser pointers from places like Roithner and one slightly dodgy looking option that claims to be 20 mW at 445 nm.

Does anyone know of a decent blue pointer (anywhere from 440 nm to 500 nm will do) at ~20 mW, or am I going to have to build my own?

camlaser said:

I'm looking for a 20 mW blue laser pointer to use as a pointing tool during astronomy meet-ups, replacing my 532 nm DPSS pointer. I already have laserbtb's '5 mW' 450 nm laser (which is actually 10 mW) but would like to upgrade the power a bit. So far I've only been able to find ridiculously overpowered 447 nm and 473 nm laser pointers from places like Roithner and one slightly dodgy looking option that claims to be 20 mW at 445 nm.

Does anyone know of a decent blue pointer (anywhere from 440 nm to 500 nm will do) at ~20 mW, or am I going to have to build my own?

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445-450nm may be too dim at 20mW for star pointing. Any reason why you're wanting to replace the 532nm?

LaserBTB do have some fairly low power 450nms though: LP 450nm 1-80

More powerful than what you're looking for but 20mW isn't going to be enough anyway, IMO.

There are two reasons I want to replace the 532 nm:

1. It doesn't work very well in the cold.
2. Green pointers are so last year...

I could get around point 1 by using one of the new 520/515 nm diodes, but that wouldn't help with point 2... Based on my tests, when dark adapted, a 10 mW 450 nm beam is more visible than a 10 mW 532 nm beam as the increased Rayleigh scattering compensates for the reduction in your eyes' sensitivity to the shorter wavelength. I don't really want to go above 20 mW (certainly not above 50 mW) for safety reasons.

I have a ~12mW blue pen, the beam is (barely) visible but nowhere near as bright as a 532nm of similar power. The only beam I've ever seen in scotopic vision was of a <100mW 405nm laser, not sure a 450nm will be able to maintain dark adapated vision.

The low power pens can be bought on ebay (this isn't the same one I have, but seems similar): http://www.ebay.com/itm/Unique-5mw-...e-Laser-Lazer-Pointer-Point-Pen-/222264066151

Atomicrox said:

I have a ~12mW blue pen, the beam is (barely) visible but nowhere near as bright as a 532nm of similar power. The only beam I've ever seen in scotopic vision was of a <100mW 405nm laser, not sure a 450nm will be able to maintain dark adapated vision.

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I have an Uncle that has a hard time seeing 405 at all. I was showing him my 300-ish mw 405, and he said that it looked grey to him. And that he could only see Violet if he looked at the dot indirectly.

I had a LaserLands "5mw" 450nm pointer and it really was nice for the price I paid (7$) but I believe it was probably atleast 20mw-50mw output as the beam was visible in dark room with fog..

Otherwise, you could look for a zombied M140 (I have one or 2 actually) which will just be an inefficient/damaged M140 to output 50-200mw.. You won't find a zombie diode anywhere but here most likely.

Lastly; I would keep 532nm for star pointing as the green seems to travel much better through the sky than a 445-450nm does, I have tons of high-powered 445-450 and they still don't seem to travel into the sky as well as my low power 532. The temp issue is easy fix.

I can see my 4-5mW Galileo in the dark just fine (532nm) and it has basically no problems with the cold, the crystal is small so it warms up very quickly. but its also a very expensive green not a cheap-o pointer. and I would do a 520 over a blue anyday though for night visibility. the increase in scatter is there, but it doesn't make up for the actual visibility generally speaking. I tend to find beam quality is more of a factor in visibility than power is. a good gaussian TEM00 1mm beam at 5mW is going to be more visible than a 4mm beam at 5mW due to the power density difference. Frankly, a 4mW green pointer is more than adequate, you just need a decent beam shape and diameter. My LG Galileo is far more visible than a new-wish cheapo of several times the power, and has little issues with the cold due to its construction generally. I hate how people always say they need more than pointer amounts of power for star pointing (and using one more powerful is technically illegal in most places. If there's little to no light pollution, it works just fine if the laser is of reasonable quality. I've even used a small green HeNe at about 1mW and it works just fine-but I can see how someone in the city would find it more hard to see, with all the street lamps and stuff....but then again...why would you want to be doing star pointing there in the first place?

just my two cents. :tinfoil:

I use a blue at 100mW for star pointing, and it's only a little bit more visible than a 10mW green. That said, it's still pretty great. I stargaze in very COLD weather, and DPSS wasn't cutting it. I have diode greens that I prefer more for that purpose now though. I just want some chrome pens to build a 40-50mW one.