November 2005 - Utah-Astronomy - mailman.xmission.com

Sky is Falling! (on 2 at 10:00)
by Patrick Wiggins 07 Nov '05

07 Nov '05

A lighthearted look at an approaching asteroid is set to air on channel 2 during tonight's 10 p.m. news. Watch if you dare... :-) Patrick

2 4

Re: Taurids
by Chuck Hards 07 Nov '05

07 Nov '05

Life's tough, eh, Debbie? ;) Do you have a parallelogram yet? > From: <astrodeb(a)charter.net> > Saturday night, I sat down in my chair at BlackRock > Rd, in AZ to look for more meteors. We saw fewer > meteors that night but the ones I saw looked kind of > like "one-armed" fireworks. By the way, M33 and NGC > 253 looked wonderful in my 15 X 70 binoculars. I was > fun not to set up any equipment and just watch the > sky for meteors or look at open clusters through the > binoculars. __________________________________ Yahoo! FareChase: Search multiple travel sites in one click. http://farechase.yahoo.com

1 0

Re: Re: Strange green lights...
by Chuck Hards 07 Nov '05

07 Nov '05

One last unsolicited comment (collective sigh of relief): Kurt is quite correct in pointing out the danger of the careful, laser-using amateur astronomer being unfairly lumped-in with those who think of these devices as toys and/or use them carelessly, possibly endangering the public. It is up to each of us to be very careful to not target aircraft, to observe laws and regulations related to laser use, and to not target people in general any closer than several miles. Having done this some 30 years ago, I was aware of the non-visibility of the beam to anyone off-axis, so with a carefully chosen path, plus my choice of set-up location (within 50 feet of the entrance to a staffed law-enforcement agency), and a safety-oriented mindset, I was not worried about causing any harm or breaking any laws. I also have used my laser from my backyard to point-out astronomical objects to my wife and daughter, again never even getting the beam close to aircraft. With forethought, and an attitude of safe use, we should be able to continue to use these tools without interference from government or an uninformed public, but it's clearly on our own shoulders to make it work. We can't be held responsible for the idiots. The same arguments for safe gun ownership apply to laser owners. __________________________________ Yahoo! Mail - PC Magazine Editors' Choice 2005 http://mail.yahoo.com

1 0

Re: Re: Strange green lights...
by Chuck Hards 07 Nov '05

07 Nov '05

With my laser mounted on the telescope, aiming was fairly precise. Next time I'll use a higher-powered crosshair eyepiece, though. Since Ann and I were in telephone contact during the test, I can say that she didn't see the beam when it was as little as forty or fifty feet off-target...here's where Michael's observation on beam integrity comes into play. A tighter beam means a brighter source when the viewer is on-axis- but still nothing visible at all if off-axis. > From: Ann House <ann(a)annhouse.org> > Well Kurt, we were but yards apart. Too bad we > missed each other. And you > would not have seen Chuck's laser light unless you > were looking directly > into it. That was something I didn't expect. __________________________________ Yahoo! FareChase: Search multiple travel sites in one click. http://farechase.yahoo.com

1 0

Re: Re: Re: Strange green lights...
by Chuck Hards 07 Nov '05

07 Nov '05

Michael, I have no way of measuring wavelength or bandwidth at present, but I'm betting that atmospheric turbulence would probably play a larger role in beam divergance over distance, don't you think?. Every distant light I saw, even in the eyepiece of the aiming telescope, was twinkling madly. Even the most coherent, narrowband wavefront would be tortured passing through that soup. > From: Michael Carnes <MichaelCarnes(a)earthlink.net> > Chuck do any of > your lasers list bandwidth as a specification? > While the nature of > the laser means that emitted light will have a > narrow bandwidth, I > can't help but think that material purity would have > a big impact on > coherence of that light. That it turn would have a > big effect on the > beam's ability to hold together over distance. __________________________________ Yahoo! Mail - PC Magazine Editors' Choice 2005 http://mail.yahoo.com

1 0

Taurids
by astrodeb＠charter.net 07 Nov '05

07 Nov '05

I was out at Anazasi Plateau subdivision near Zion National Park Friday night with my 15" telescope. Jim borrowed my camera to image M31 and NGC 253. While we were there, we saw several bright meteors streaking through the sky. Some burned as much as 30 degrees across the sky. We must of seen at least a dozen or so meteors Friday night. We plan on going back out there at the end of the month. If anyone is interested in the Anazasi site for some prime winter observing, let me know. Saturday night, I sat down in my chair at BlackRock Rd, in AZ to look for more meteors. We saw fewer meteors that night but the ones I saw looked kind of like "one-armed" fireworks. By the way, M33 and NGC 253 looked wonderful in my 15 X 70 binoculars. I was fun not to set up any equipment and just watch the sky for meteors or look at open clusters through the binoculars. Debbie

3 3

Re: Re: Strange green lights...
by Chuck Hards 07 Nov '05

07 Nov '05

A variation on the Boy-Scout project, eh? Michael was on the right track. By the time the beam hits the first mirror, it's probably yards across and the distended, expanded dot is probably invisible to the naked eye. A small mirror would only reflect a tiny percentage of that- now multiply the loss by every mirror in the train, and soon not even sensitive detectors could discern the laser. > From: diveboss(a)xmission.com > Why not set up a bunch of mirrors around the valley > and see if 1 laser can hit > them all... __________________________________ Yahoo! Mail - PC Magazine Editors' Choice 2005 http://mail.yahoo.com

3 3

Re: Re: Strange green lights...
by Chuck Hards 07 Nov '05

07 Nov '05

Michael, Bill Kelley would rescue this project. No need to figure a large shallow mirror...just flex a big aluminized flat mirror. Of course, mechanical sag would probably swamp any intentional flex on something that large and that close to flat. Maybe an array of smaller mirrors would be better? And then we woke up! ;) > From: Michael Carnes <MichaelCarnes(a)earthlink.net> > Guy's idea about multiple mirrors is interesting, > but it would sure > take some mighty fine mirrors. Any of the ATM's on > the list have an > interest in grinding FLAT mirrors? Actually, > slightly parabolized > might be better, in order to reconverge the beam. > Let's see, 20 > miles with a six-foot mirror. That's a little over > F/17000. Any > takers? __________________________________ Yahoo! FareChase: Search multiple travel sites in one click. http://farechase.yahoo.com

2 1

Re: Strange green lights...
by Chuck Hards 06 Nov '05

06 Nov '05

> From: Canopus56 <canopus56(a)yahoo.com> > For a Class IIIA, that's probably too far. 3.5 > kilometers is FAA tested "no effect" limit Too far for what? Ann's laser was easily the brightest light in the valley, seen from my location, when I was on the beam axis. Maybe "no effect" means something other than "no visibility" in this instance? No time to check references this morning, sorry. I'll impose on you to educate me here. > Chuck, not to put a damper on your activities and > enthusiam - which I respect immensely - but since > you > live in a landing corridor and are projecting across > the 5-7 kilometer FAA "laser free" zone around SLC > Int'l Airport, technically, what you are doing might > violate FAA flight orders. No worries, you didn't put a damper on anything. Being on the digest, I didn't even see your post until Sunday morning at 11:30. And even then, I respect your proclivity for thoroughness and attention to detail, and would worry if you hadn't found a regulation relating to this! ;) But I'm not worried about a visit from Men In Black. I first did this in about 1975, with a much more powerful laser and my parent's assistance, so I was fairly sure of the outcome. This time it was green instead of red, however, and the laser was much, much smaller! There were probably no FAA laser regulations at all back then. And my line-of-sight was very, very similar. This time, I was just west of Redwood road, well east of the runway axis, probably near the southern limit of the 5-7km zone, aiming no higher than 3-5 degrees and in a northeasterly direction- there was no chance of my beam being seen -at all- by any aircraft on-approach to SL Int'l. Ann was probably near the eastern limit of the zone, and projecting toward my location at the southern extreme- and she was aiming at an angle below the horizon- so I doubt that any aircraft at all could have seen either beam, with the exception of perhaps a Lifeflight, TV news, or constabulatory helicopter, which we were on the lookout for. I suppose if an aircraft were low enough to clip the trees or a cell tower, the pilot might have seen a green flash, but he'd have other worries. I don't mean to minimize FAA regulations, but we took reasonable precautions, chose our line-of sight carefully, and are very aware of the concerns of aviation regulatory agencies. This wasn't a "lets go out and flash our lasers around" kind of thing, or a high-powered commercial light show. > P.S. - I live in the Avenues, so I'll stick a pair > of > binos on Ensign around 8:00PM. I doubt you saw anything. While the beams don't diverge that much, after seven to nine miles it's still wide enough to not be noticed on a dark, irregular background such as a hillside- the "dot" is probably fifty or sixty feet across by then. You'd have to be on-axis to see it. Next time, lets talk in advance and if you have line-of-sight to my location, I can target you, too. And just to play it by the numbers, I'll shift my site eastward to stay well clear of SL Int'l...and airport #2. Point-of-the-mountain might work well. I do need to work on my hardware, though, to make it easier to both collimate the laser with the telescope, and aim the telescope more precisely. Tripod pan/tilt heads are not a good enough choice, and neither are manual Dob mounts. An equatorial with slow-mo controls would be ideal. __________________________________ Yahoo! Mail - PC Magazine Editors' Choice 2005 http://mail.yahoo.com

5 6

Re: Strange green lights...
by Chuck Hards 06 Nov '05

06 Nov '05

> From: diveboss(a)xmission.com > How far apart will you be? Guy, a separation estimate would be about nine miles, as the crow flies. I'll check it more precisely soon and let you know. I believe Ann will agree with me in saying that our first attempt was a great success. The laser light was easily the brightest light seen from my point of view when directly targeted. I could see Ann's location through the small refractor I used for aiming purposes. She flashed a regular flashlight that let me place my dot just about on-target. She can describe for herself what she saw from her location. >From my vantage point, I saw her laser easily- you couldn't help but see it! In the telescope, the diverging beam itself could be easily detected sweeping around-an eerie effect reminiscent of "War of the Worlds". I couldn't see the beam with the naked eye, just the source. When it was just off-target it was still visible but not brilliantly bright, as when we were inside the beam itself. I used a remote switch to keep from moving the telescope when I was flashing the laser. I only kept it on for less-than-30-second intervals and usually flashed it slowly but regularly. I used my Beta Electronics optimized 5mw unit on a vee-block mounting arraingement on a small refractor. Prior to the test, I mounted the laser on the telescope and projected the dot on a fence about a block away, then shimmed the laser until the dot was dead-center in the field-of-view of a crosshair eyepiece. I left it undisturbed until the test tonight. It was then just a matter of finding Ann's flashlight in the eyepiece, then superimposing the crosshairs on her location and turning-on the laser. Of course it wasn't that simple- the cold made the tripod pan/tilt head I was using a bit sticky so precise adjustments were more difficult to make than in my living room hours earlier. But it was adequate for a first try. I also flashed my "3-5mw", $42 Computer Geeks unit at her, hand-held. Her remarks to me on the cell phone were to the effect that it seemed as bright as the high-dollar unit, but she'll have to elaborate there. Of course it was impossible to keep the hand-held unit on-target steadily. I also discovered that the batteries in my Beta unit were dying near the end of the approximately 20-minute test. They were the original cells that came with the laser and there is no telling how long they were sitting on a shelf before being sold. They were also an off-brand (Toshiba) labeled for the Asian market. Next time I take fresh spares. I exposed two frames of ASA400 with a 50mm lens, if one of them turns out I'll scan it and post it to my Gallery page. >From this experience I can say that a 5mw laser pointer is no hazard to an aircraft flying at 30,000 feet. Just keeping it on-target while hand-holding it would be a remarkable task in itself. The only way I could keep Ann targeted tonight was because we were in cell-phone contact and she told me when I was pointed at her. And she was stationary- staying on a moving target would be incredibly difficult if not impossible. And even on-target, it was not too bright to look at. It was very bright, brilliant, even, but not uncomfortably so. Entrancing, attention-getting is more like it. I think the only hazard to aircraft would be those on-approach, at much lower altitudes. Say two miles instead of nine or ten. Read Kurt's paper for more information on the effect of lasers at close range. For future attempts I'm going to improve on the laser/telescope interface itself, and use my equatorial mount with precision slow-motion controls, for more precise micro-adjustments. I'd also like to try it the full length of the valley- say from Steve Dodd's neighborhood to Ann's, more like about 30 miles. Did anyone else happen to notice the laser light flashes tonight? If so, what did you see and what was your location? All in all this was an interesting, FUN activity on an otherwise cold, cloudy night. __________________________________ Yahoo! FareChase: Search multiple travel sites in one click. http://farechase.yahoo.com

2 1