Hi Jim, you always are a voice of reason. I think the kernal of Kevin's post was that super-bright lasers are overkill at dark sites, especially a remote site where some people have specifically travelled a long distance just for dark night skies and fabulous natural daytime scenery. In those places, a low-powered laser should be sufficient. Laser users should always be mindful and respectful of the activities of others in their vicinity. Not many people know that many diode lasers in the range from 5mW up to almost 30mW are actually the exact same diode as the 5mW or less lasers. There is inconsistency in manufacture and some 5mW units have an output closer to 20 or 30mW. But legally, it's still a 5mW laser. An importer has not broken any laws by selling these units- they leave the factory as 5mW lasers. We need to remember that lasers do not of themselves cause problems. Like firearms, it's the person wielding it that commits the crime. Some murders are committed with baseball bats, but nobody wants to legislate Little League out of existence. Like anything, education is the key to proper use. I believe one person on this list used their super-bright laser pointer at a native American ceremony in Southern Utah, when the local shaman's laser's batteries died just before the show. A non-astronomical use that sure sounds legitimate to me. And the next time I go hiking in a wilderness area or other remote location, I will take the brightest laser I own, as an emergency signaling device. 100mW is enough to be seen miles away, in sunlight. As to the issue of a laser pointer possibly ruining an exposure during imaging (really a time waster these days since no film is ruined), let's do some experiements. I'll volunteer a couple of lasers if someone else wants to do the test imaging. Let's get some real data. On Thu, Feb 19, 2009 at 5:46 AM, Jim Gibson <jimgibson00@yahoo.com> wrote:
Chuck, A good common since answer. I hope green laser pointers don't become an off topic on this list. I feel that there are places when green laser pointers are appropriate and a legitimate teaching aid. It wouldn't hurt from time to time for the benefit of newer folks to cover green laser etiquette. I am probably not the one to do that because I can't remember everything, but we have had good discussions on this list when the use of green laser pointers are not appropriate. Generally speaking there should be no problem using a green laser pointer in your backyard while showing neighbors astronomical items of interest. However, in a public place where tourists are milling around it may not be appropriate. It MAY be appropriate at an SLAS star party, but one should ask the group before using a green laser pointer because others may be imaging or have some other objection.
A few times a year I take my kids and their kids to Rush Valley for a little sundown pizza and to do a little family star party after dark. Invariably someone will ask me where or what is my telescope pointing at. In such circumstances a green laser pointer adds to the joy and learning of observing the night sky. Kids don't always see asterisms that have become obvious to us; a good situation for a laser pointer, but one must consider the circumstances and who else is around.
Jim
--- On Wed, 2/18/09, Chuck Hards <chuck.hards@gmail.com> wrote:
From: Chuck Hards <chuck.hards@gmail.com> Subject: Re: [Utah-astronomy] Fw: New from JasperLaser.com: 50mw and 100mwgreen lasers! To: "Utah Astronomy" <utah-astronomy@mailman.xmission.com> Date: Wednesday, February 18, 2009, 8:41 PM
Kevin, there are legitimate reasons for using a laser brighter than the typical 5mW output. None of them apply to someone lucky enough to have dark skies every night. Perhaps a park rule could be enforced for your situation. It's far removed from my astronomical world.
I started with a 5mW laser, which was fairly visible from a dark site. From the suburbs, where most of the star parties I've ever been to have been held, 5mW is not bright enough. Only those fairly close to the beam axis can clearly see it. From a Harmons parking lot, for example, forget it on some nights. Yes, sometimes they are sufficiently visible, but not always. A lot of dust or water vapor in the air contributes to beam visibility.
A 20mW laser is much better from the suburbs, but not for large groups. On some nights when the air is particularly transparent, such as after a frontal passage, even the 20mW laser visibilty suffers.
The 100mW laser is easily visible to all star-party attendees from even heavily light-polluted, urban locations. Places where there aren't even enough visible 4th magnitude stars to verbally describe where the telescope is pointing. Attendees with poor vision, even those with "low" vision have been able to see the 100mw beam with ease.
Astro-imagers are far more likely to have their images ruined by night-flying aircraft or satellites, than a laser pointer. Visual observers are typically not affected, based on my own, admittedly non-scientific visibility tests held at SPOC two years ago with a 20mW laser pointer.
I believe the planetarium director owns a 100mW laser, purchased expressly for use at public star parties. A former SLAS president owns a 50mW laser, again purchased solely for it's excellent visiblity. Both have stated that 5mW lasers had very limited use as educational pointers. Neither of these people found themselves at truly dark sites for the majority of the star-parties they lectured or assisted at.
A 5mW laser is just as capable of blinding the operator of a ground vehicle or aircraft if misused, as a higher output device. Perhaps pilots could be encouraged to wear laser safety glasses (less than $50 ea., typically) for landing, if they are concerned. I'm sorry, but the "keep the power down" stance does come off as sanctimonious to me, when applied this broadly. I certainly won't use one within the confines of Bryce Canyon, however, or any other sufficiently dark site.
A reminder that in Utah <http://en.wikipedia.org/wiki/Utah> it is a class C misdemeanor <http://en.wikipedia.org/wiki/Misdemeanor> to point a laser pointer at a law enforcement officer<http://en.wikipedia.org/wiki/Law_enforcement_officer>and is an infraction <http://en.wikipedia.org/wiki/Infraction> to point a laser pointer at a moving vehicle.[33]<http://en.wikipedia.org/wiki/Laser_pointer#cite_note-32>
Kim, the laser will dim when either the temperature gets too cold or the battery output drops below a certain level. It happens to mine, too. _______________________________________________ Utah-Astronomy mailing list Utah-Astronomy@mailman.xmission.com http://mailman.xmission.com/cgi-bin/mailman/listinfo/utah-astronomy Visit the Photo Gallery: http://gallery.utahastronomy.com Visit the Wiki: http://www.utahastronomy.com
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