Tips for outdoor use
There are at least two potential consumer uses for lasers outdoors:
- Pointing out stars in the sky: This needs to be done with caution. It is an application that requires relatively strong lasers, so that viewers can see the beam shaft (not just the end dot). Further, the beam is aimed at glowing objects in the sky. Because these glowing, point-like objects could be aircraft, outdoor laser users need to be careful.
- Dispersing birds: LaserPointerSafety.com does not recommend that ordinary consumers use lasers to scare away unwanted birds. The right type of laser with a wide, low-powered beam is not available so there are too many potential safety problems for the birds, for the laser user, and for bystanders. Also, there is a chance of accidentally having the beam be on or near an aircraft; this is illegal in many countries and jurisdictions. Finally, some species of birds may be only temporarily repelled by lasers; after a few minutes or within a day, studies indicate they will return.
Both applications are discussed in more detail below.
Star pointing tips
Don’t point; circle instead
Aircraft at a distance can look like stars. This is especially true if they are moving towards you, since there will be little apparent motion.
For this reason, NEVER point directly at a dim or unknown “star”. Instead, move in a circular motion around the object. When doing the circular motion, or when “drawing out” a constellation, keep the beam moving and keep it away from any stars. The “stars” may be aircraft.
Use the laser only long enough to point out the object. Once it is identified, leave the laser off. (After all, this is how people observed the sky for thousands of years, before laser pointers were invented!)
The beam does NOT end!
This unretouched photo shows how a beam outdoors can seem to end after only a few hundred meters. This is a potentially dangerous illusion, as described here. The beam actually continues to travel -- even though the viewer can no longer see the light scattered back to them.
In Feb. 2011, a 14-year-old boy was arrested for illuminating an aircraft on approach to Los Angeles International Airport. He told police that he thought the beam “would not go up to the height of the aircraft.” He was wrong, of course.
Instead of a few hundred feet, a beam can be a hazard to pilots miles away. For example, even a relatively weak U.S.-legal 5 mW laser pointer is a distraction hazard to pilots over two miles away. The more powerful beam in the photo can cause serious glare (the pilot can’t see past the light) two miles away, while the distraction hazard is 22 miles!
Therefore, ALWAYS act as if the beam continues on, forever. Don’t let the beam get close to any aircraft or unknown star along either the visible beam path OR its non-visible continuation.
(Quick explanation of the illusion: There are two effects happening. One is that at some point, the beam exits the dustier part of the atmosphere. This means much less light is reflected back. You can no longer see the beam when it is in cleaner air, higher up. The other effect is that while the beam is slowly spreading out, perspective -- like train tracks appearing to converge far away -- counteracts this, so the beam appears as if it is always parallel. An “infinitely parallel” line is unfamiliar to our visual system. We therefore misjudge the beam’s length; a beam that can be seen miles away may appear to the laser owner as if it is only a few hundred feet long.)
For star pointing, green is best. The human eye sees green much better than the same amount of red or blue, so a 5mW green laser appears to be 5 to 10 times brighter than a 5mW red laser.
Looking at a green beam in the sky should not adversely affect night vision. To keep your night vision, avoid looking directly at the laser dot on a nearby or light-colored surface.
5 mW works fine
In some jurisdictions, there are limits on laser power. For example, in the U.K. it is not allowed to sell laser pointers over 1 mW. In the U.S. it is not permitted to sell lasers for pointing applications over 5 mW. You may be restricted, therefore, in the laser pointers which are available to you.
However, you may be in a country without laser restrictions. Or you may obtain a laser which was not sold or intended for pointing but which nevertheless could be used outdoors. The question then is “how much power is needed?”
For yourself or a small group under most conditions, 5 mW is sufficient. For a larger group, or where the air is especially clean and dry, slightly higher power such as 10 to 25 mW will be better. The absolute limit for this application should be about 50 mW. There is no objective reason to need more than 50 mW for astronomical pointing applications.
Here is one user’s description of the visibility of his 4.92 mW laser pointer:
- “The first time I used it, I was in a rural area, although not very far from the city, and there was a setting gibbous moon. Limiting magnitude was around 5.0, maybe 5.5. The laser was bright and easy to see.... can you see it from a dark spot in the worst light-polluted sky imaginable? Yes, you can see it. Just for perspective, I used it about 45 minutes after sunset. The sky was still quite bright, with 20 minutes of nautical twilight left, and an hour of astronomical twilight. Limiting magnitude was perhaps 3.5. The beam was visible in these conditions. Dim, but unmistakably visible.”
Tips and resources from astronomers
The Royal Astronomical Society of Canada has produced a webpage with information and recommendations on green laser pointer usage. At the bottom of the RASC webpage are additional resources such as a brochure, poster and PowerPoint presentation.
The Astronomical Society of South Australia has a similar document, Guidelines for the Safe Use of Hand Held Laser Pointers in Astronomy. It includes a form “to assist the police or other enforcement Agencies” by providing evidence of membership in the ASSA; the form should be carried by ASSA members “at all times when the laser pointer is in their possession.”
Bird deterrence and dispersal
Some consumers have asked about using lasers for bird dispersal.
A September 2003 U.S. Department of Agriculture publication, “Use of Lasers in Avian Dispersal” says that lasers are “safe and effective species-specific alternatives to pyrotechnics, shotguns, and other traditional avian dispersal tools.” A key phrase is “species-specific”. For example, a 2002 USDA study of crows (listed below) concluded that lasers do not work for more than a few minutes of dispersal, and are therefore not recommended for crows.
LaserPointerSafety.com believes there is a difference between serious, professional use, and consumers ordering possibly over-powered lasers off the Internet and simply waving them into trees and the sky. This is especially true in today’s environment where authorities are very sensitive to lasers being aimed into the air by ordinary citizens.
Our recommendation is that consumers should not use lasers against birds, especially Class 3B and 4 lasers (output power of 5 milliwatts or above). If a person feels they must try this, it should be done very carefully, with continuous monitoring of the sky so that aircraft are not accidentally targeted.
Discussion of a commercial bird dispersal laser
The following is based on information from the TOM500 Bird Deterrent Laser System developed by LORD Ingenierie of France.
The TOM500 laser is much more than a pointer.
For one thing, the system weighs almost 1000 lbs.
The TOM500 uses a green laser wide beam roughly 6 inches in diameter, which constantly sweeps a few inches or feet above airport runways. The beam enlargement does two things:
- The beam looks like a stick to the birds, according to LORD. They see this “stick” and disperse.
- Enlarging the beam helps make the beam bright but safe. The laser is rated at Class 2M. Class 2 means the direct beam is eye-safe for a short (1/4 second) unintentional exposure due to humans’ natural aversion to bright light. (The “M” part means that optical aids such as binoculars or telescopes should not be used to view the light, since it could be concentrated to a potentially hazardous level.) The TOM500’s power is 0.7 milliwatts into a 10 mm diameter aperture. The human eye’s night-adapted pupil is about 7 mm, so even less light would enter the eye.
However, such large-beam, low-powered lasers are not readily available to ordinary consumers. Tight-beam, high-powered lasers are much more common. Using such a laser with birds may be a hazard to the animals. Certainly, any Class 3B or 4 handheld consumer laser (for visible lasers, above 5 mW) is an eye hazard to humans. You would not aim these at persons, so it stands to reason that birds’ eyes could possibly be harmed depending on the laser power.
Other laser-related dispersal products and information
Note: We do not necessarily recommend consumer use of these products or techniques, especially since aviation officials are sensitive to unsupervised use of lasers in airspace. The items below are listed for informational purposes.
- An Australian company makes the Bird Gard laser gun, intended specifically to scatter birds. The user manual states it has 50 mW output, 650 nm (red), with a large 50 mm beam at the aperture. The Nominal Ocular Hazard Distance is 300 feet (90 m) which means the direct beam should not go into a person’s eye if they are within 300 feet of the laser gun. Species listed for this laser gun include black duck, cormorant, heron, ibis, pigeon, sparrow, swallow and wood duck. The Bird Gard laser gun webpage has a short video showing birds being dispersed by the red laser light.
- A December 2002 U.S. Department of Agriculture publication discusses “Evaluation of lasers to disperse American Crows … from urban night roosts.” The University of California at Davis conducted a study over four nights. From 50% to 99% of crows did disperse due to laser light being aimed at them. But they came back within 15 minutes. Even after four nights of laser harassment, the crows still returned to their roosts. The authors wrote “The laser beam produced a startle reaction comparable to that produced by a sudden, loud noise, but imparted no threat sufficient to cause desertion of a roost.… we do not recommend lasers as a stand-alone dispersal tool at urban crow roosts based on the poor results…” The study did imply that other species might react differently: “Little is known about the reaction of most North American bird species to laser light or the most effective application of lasers for different species and locations.” The study also noted possible problems with aircraft. It reported on one 2000 study where after two hours of lasing a tree, crows stayed off for one night: “However, further treatment on successive nights to determine if birds would abandon roosts could not be undertaken because of aircraft traffic at an adjacent airfield.”
- A January 2002 article in the Journal of Wildlife Management, “Lasers as Nonlethal Avian Repellents”, contends that lasers may prove useful but more research is needed on the powers, wavelength, etc. that are most effective against various species. The study does report some controlled tests in which it seems most birds returned within 20 minutes to the laser-treated area.
- A February 2002 review of lasers for dispersing birds around airports, presented at a 2002 FAA conference, concludes that “low- to moderate-power, long-wavelength lasers (630- 650 nm) provide an effective means of dispersing some ‘problem’ bird species under low-light conditions, while presenting no threat to the animal or the environment.” (The FAA presentation was not peer-reviewed; it represented work that was published in the January 2002 article listed immediately above.)
- A 2006 study of deer found that lasers would not be effective for wildlife management. Results showed that while deer could see the laser spots, they “appeared to be more curious than frightened. We conclude that laser light has no potential as a nonlethal management option for reducing deer damage.”
- An August 2013 news story briefly describes how the manager of a golf course uses a laser pointer to disturb nuisance geese that soil the course: “They would come in every morning at 5 a.m. and wake me up. I would go out with a laser and shine it across the lake, and they were gone.”
Thanks to Dr. Mathieu Gauthier for sending in a correction to this page on 2/23/2012.