5mw laser plus star maps. Credit: Dave Dickinson

Tired of waving towards astronomical targets blindly in the dark? Once my wife saw a green laser pointer in action at a local star party, she knew what I needed for Christmas.

Though laser pointers come in a multitude of colors, the very best in terms of visibility are tuned to green wavelengths around 532 nanometers. What you’re seeing when you use a green laser pointer is the concentrated beam of light reflected off of dust and aerosol particles suspended in the atmosphere.

Jupiter, Venus and laser. Credit: Dave Dickinson

Though laser pointers are primarily used during public outreach to show off the sky, I’ve also seen them used effectively as finders or pointers – either boresight-mounted along the tube of a telescope, or used in tandem – as a spotter points the beam where the telescope operator needs to aim.  

Though laser pointers are handy for public outreach, they are also hazardous in the wrong hands. The main problem with laser pointers is that they look too much like lightsabers out of Star Wars. I always keep my laser pointer on a short tether at public star parties, and answer the inevitable queries of “can I see that?” with a polite but firm “no.”

Along with solar observing, using a laser pointer is probably the most dangerous thing we do in amateur astronomy. Even a standard 5-milliwatt laser pointer can temporarily blind someone out to a range of 262 feet (80 meters), and can do permanent eye damage at close range. Never aim a laser at an aircraft or passing automobile, even for a second. In fact, never aim it below the horizon, period: you never know who might be standing off in the dark. Also, be wary of accidentally shining a laser off of a reflective surface into someone’s eye.

Safety diagram: Wikimedia Commons: https://en.wikipedia.org/wiki/File:Laser_pointer_safety_distances.gif

There are laws in the U.S. in many states making it a felony to aim a laser pointer at an aircraft, and violators have been tracked down, prosecuted and fined in recent years.  Also, be sure to put your laser in checked baggage if you’re traveling to do astronomy, and be sure to check the local laws at your destination. Some European Union countries, for example, restrict handheld lasers at 1-milliwatt, and with lasers turning up at protests in the U.S. and abroad as of late, expect those restrictions to tighten.         

What’s New on the Market

There’s a flood of cheap laser pointers now on the market, including models that are USB rechargeable…but caveat emptor (buyer beware): A 2013 U.S. Commerce National Institute of Standards and Technology (NIST) study demonstrated that many laser pointers advertised as ‘5-milliwatt’ are actually way overpowered. Some commercially available lasers are actually in the 50-milliwatt military-grade range or higher. For astronomical applications, up to 20-milliwatt is more than enough, and I would definitely stick with the lower 5-milliwatt range for public outreach when shopping around.

Lasers for astronomy on the market include Maymoc‘s Green Laser Dot Sight, the Suphunter Tactical Green Laser, and Iron Jia‘s Compact Adjustable Dot Laser. Orion, Celestron and OPT Telescopes all have or offer consumer laser pointers optimized for astronomy, mostly in the $20 to $500 USD price range. LaserPointerPro also offers laboratory grade lasers up through the 6000mw (6-watt!) range, but again, this is probably more laser than you’ll ever need to simply aim at the sky.

I’ve also found that green laser pointers in the 5-milliwatt or less range (a typical Class IIIa laser) work  just as well with rechargeable nickel-metal hydride batteries as with standard alkaline batteries. Incidentally, the laser pointer I’ve used now for about 20 years was made by Leadlight Technology, a company that no longer exists.

LIGO Hanford safety goggles. Credit: Dave Dickinson

What else can you do with a laser pointer? Well, a San Antonio-based astronomy club coordinated a successful signaling project with astronaut Don Pettit aboard the International Space Station in 2012, using flood lights, large plywood boards… and a 1-watt blue laser.

Whatever the case, be sure you employ your green laser pointer as the right tool for the job… and know just how to safely and effectively use it. For more information, you can review my Universe Today articles on the hazards of green laser pointers.

 

About David Dickinson

David is a freelance science writer, frequent contributor to Sky & Telescope and Universe Today, author of several astronomy books and long-time amateur astronomer. He lives with his wife Myscha in Norfolk, Virginia.

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