125mw laser

Recently I purchased a 125mw green laser.  You can see my previous posts on this here, here, here, and here

On May 31, I took my new 125mw laser and the trusty 5mw laser up to Fremont Peak for a public program.  I was able to use the 125mw and cast a visible beam as soon as we could see Saturn.  I couldn’t see the 5mw at all, but the 125mw was bright enough even in the civil twilight  to cast a visible beam and aid in aiming the Challenger.

The 125mw was a big hit with the other astronomers.  I was able to point out objects with it for about an hour before the 5mw lasers became visible.  “Oohs” and “Ahs” were abundant, even from the other astronomers.

Remember, if you purchase one of these, you really should take the warnings seriously.  A 125mw laser can blind someone if it reflects off of a mirror surface (specular reflection) and hits them in the eye, and FAA regulations state that this class of laser device is illegal within 20 miles of a commercial airport.

This is not a toy

image Ok, fancying myself as an Über-geek, I just had to have one of the new 125mw green lasers. The first one I ordered from techlasers.com apparently got waylaid by the FDA in Louisville KY, but a message to the support people at TechLasers had a replacement on its way to me the next day. I’ve had this laser in my hands for about 48 hours now, and I’m compelled to write a review of it.

WARNING: A 125mw laser is a Class-IIIb radiation emitting device. Misuse of these can blind you! The radiation from one of these, if it were to reflect off of a shiny surface, or even a bright white matte surface (like paper) can damage your retina permanently.

Short version: WOW! This is one BRIGHT laser!

Long version: This is not a toy. This is a serious laser. This should not be used in any situation where reflections are possible, unless everyone within view of the laser is wearing appropriate eye protection. YouTube videos of lasers in this class show people lighting matches, popping balloons, and melting through electrical tape. As tempting as those things are for the sheer ‘coolness’ factor, doing any of them with this laser is DANGEROUS and I do not advise it! Do not use this laser as a ‘laser pointer’. A 1mw red or up to 5mw green laser pointer works just fine for that.

I’ll be comparing this laser with my 5mw 532nm laser from Zhumell, which has been my primary astronomy laser up to this point.

The laser is 5 7/8″ (15cm) long, with a shiny black finish and bright brass battery and aperture caps. The tube diameter is 1/2 inch (1.3cm) and there is a brass pocket clip attached to the battery cap end. A rubber button protrudes from the side of the tube 90 degrees clockwise from the clip, about 2 inches (5cm) from the aperture cover.

The battery cap unscrews counter clockwise to open the battery compartment. Two 1.5 volt AAA batteries power the unit. The batteries go in negative (flat end) first. The exposed part of the battery cap is only about 3mm tall, and is smooth and curved. In order to open or close the battery I had to grip the battery cover very tightly. The Zhumell laser battery cover (which has the actuator switch integrated into it) is about 8mm tall, and knurled, so it is much easier to grasp it.

The tube body appears to be brass, and appears to be very thin. However, I was not able to deform it from round using finger pressure at all, so the brass used appears to be hard enough to support the tube during normal usage. With the batteries in and the battery cover on, it feels sturdy. A second brass liner tube begins below the level of the clip attachment and holds the batteries snugly in place. The battery cap has a machined recess to accept the positive electrode on the battery and extends down over the top of the second battery to hold it in place. With the batteries in place and the cover on, there is only slight movement of the batteries within the tube during vigorous shaking. Note that a too-snug battery tube would be bad… batteries have a bad habit of expanding if they are overheated, and then you’d be unable to get them out of the tube.

Turning my attention to the ‘business end’ of the laser, I removed the batteries for safety, and then examined the aperture. The aperture cap is another simple brass cap with a hole through the center. It unscrews to reveal the laser module, which is threaded into the tube. The aperture of the laser module is covered with a small coated lens which likely also serves as the IR filter. The entire laser module is set back from the aperture cap by about 1cm, and the lens itself is in a recess about 1cm deep in the laser module.

The actuator button is about 5cm back from the aperture end of the laser. The button is oblong, about 6mm by 5mm, and protrudes slightly (2mm) from the surface of the tube. My comment on the button is that this arrangement makes me nervous about carrying the laser in anything except the original box, and/or with the batteries uninstalled, as unintentional actuation of the button appears to be easily possible. The Zhumell button is integrated into the battery cover, and is recessed, making unintentional actuation much less likely. I have seen other lasers on the market where the actuator button is recessed into the side of the body, also helping prevent accidental actuation.

I put everything back together, and started trying it out. This laser is very strong. I could project a visible dot onto a structure over 100 feet away in broad daylight. At night the beam was much more visible than the 5mw laser, and appeared to reach much higher into the sky. During a well moonlight night (waning gibbous, 60%) the beam from the 125mw laser was easily visible where the 5mw laser beam was washed out anywhere near the moon.

During use the purpose of selecting a momentary switch over a latching switch became apparent. After about 30 seconds of continual use the laser module became palpably warm. The TechLaser website states that this laser is rated for continuous use up to 100 seconds.   Of course, the constraints in heat dissipation for a small laser module like this are severe.   The larger lasers available from this manufacturer have large heat sinks around the laser module for this reason.

What am I going to use this for?  Primarily astronomy on moonlit nights where my 5mw would be washed out.  However, I’ll definitely be taking more precautions than I used with the 5mw laser.

Overall my impressions with this laser are very favorable.  It is a high powered 125mw laser suitable for astronomy (provided suitable precautions are taken).   I would have liked to see a couple of minor design changes such as a knurled battery cap, and a recessed actuator button, but I’m very happy with the output power and overall quality of the unit.  My rating is 4 1/2 out of 5 stars.