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Global Green Laser Pointer

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Red lasers have become ubiquitous in today’s world. After all, every CD player has one. They are cheap to produce. Why then, do you see green laser pointers going for $70 and up in astronomy magazine ads? Well, it turns out, green is a much more complex color to make. Viable diodes don’t exist in the proper wavelength, so the laser beam is “pumped” through a pair of crystals that must be accurately collimated. (There is even more to the process, and a longer, even more boring explanation is available on Wikipedia for those interested, but suffice to say that collimation will complicate anything, and hence add to cost.)

Imagine my surprise, then, when Yugster.com was selling one for $16. (This drop may be due to the fact that blue lasers, used in increasingly common Bluray players, use the same construction principles as green.) I had always wanted to play with one, but this brought one into impulse buy territory for the first time. (Yugster only sells one item per day, but I have seen this item repeated since I bought it). It is made by Global, a British company, and runs on two AAA batteries, so no expensive, exotic batteries to find. This makes the tube almost 6” long, though, but only only ½” in diameter. This actually makes it comfortable to hold in the hand, and might make aligning it in a rig for a non-magnified finder easier. I have not tried it as a finder, as I already use a Daisy finder I made several years ago.

Now, why would you want a green laser? In short, because you can see the beam. Unlike a red laser, which generally reveals itself as a small dot on whatever it hits, a green laser shows a long green line from the source out into the sky. This is due partially to its power, which is vaguely referred to as <5mw. Red laser pointers are typically Class 2, less than 1mw. This one is Class 3A, 1-5mw. Green lasers are available in higher powers (at higher cost, of course), but cannot legally be sold as pointers, at least in the USA. Also, the human eye is more sensitive to green than red, so even at matching power, green will appear brighter. Rayleigh scattering, which turns sunlight into blue sky, and scattering by dust particles in the air, are enough to make the green beam visible in any moderately dark situation. It won’t work in daylight, but you really don’t need a laser pointer to spot the one star visible in the sky then. Dark skies aren’t mandatory either. Light polluted urban skies are fine. I live in the relatively clean air of Central Florida, but certain urban areas may have enough surplus “dust” to actually enhance the scattering effect.

In use, the beam extends far enough into the sky to be useful as a pointer.

As I said earlier, it may be viable as a scope finder, but don’t expect to use it for long at a star party. You and/or your scope may not escape the wrath of a neighbor in the middle of a long-exposure session. It is a natural, though, in a group educational setting, where finger-pointing is usually just not accurate enough to convey position for anything smaller than the moon. It also just looks cool, so may keep the attention long enough of any attendees not at your educational soiree voluntarily for some of your valuable information to sink in. This use may or may not be a common application for you, but at this price range, the cool factor alone may be enough justification. Just remember that it is a more powerful laser than your typical pointer, so responsible use is needed. I have never shone it into anyone’s eyes, so can’t tell you its effects, but I imagine there is a reason why lasers beyond this range are more tightly regulated.

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