Re: [Utah-astronomy] Re: Green laser special - $35
Seems like beam coherence (spread over distance) might also be a good thing to measure. That's the only thing that might require some space.
Remember that it was designed to yield useable information and isn't simply a "mine's brighter than yours" thing.
Don't you think that coherence will be a contributing function to brightness? --- Michael Carnes <michaelcarnes@earthlink.net> wrote:
Seems like beam coherence (spread over distance) might also be a good thing to measure. That's the only thing that might require some space.
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Make that "factor", not function. Could be interesting, but we'd need a lot of distance between the laser operator and the person with the ruler. Also, a spot size small enough to measure directly would probably mean a hazardously bright environment directly in the beam. Kurt, you've researched lasers over relatively short distances, what do you think about this? --- Chuck Hards <chuckhards@yahoo.com> wrote:
Don't you think that coherence will be a contributing function to brightness?
--- Michael Carnes <michaelcarnes@earthlink.net> wrote:
Seems like beam coherence (spread over distance) might also be a good thing to measure. That's the only thing that might require some space.
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I don't know why a comparison of pointers needs to be such a big production. In choosing laser sights for weapons, you simply point the competing laser sights at a wall and go with the laser that produces the brightest and smallest spot. Quoting Chuck Hards <chuckhards@yahoo.com>:
Make that "factor", not function.
Could be interesting, but we'd need a lot of distance between the laser operator and the person with the ruler. Also, a spot size small enough to measure directly would probably mean a hazardously bright environment directly in the beam. Kurt, you've researched lasers over relatively short distances, what do you think about this?
--- Chuck Hards <chuckhards@yahoo.com> wrote:
Don't you think that coherence will be a contributing function to brightness?
--- Michael Carnes <michaelcarnes@earthlink.net> wrote:
Seems like beam coherence (spread over distance) might also be a good thing to measure. That's the only thing that might require some space.
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Brightest and smallest spot aren't always found in the same laser, and this is more of an issue in an astronomical pointer than a firearm aiming device. This relates to Michael's question of divergence. These things are usually used to point at infinity, and I bet your marksmanship isn't quite that good. Also, recall what I wrote about variation between individual examples of the same model pointer. By examining as many examples as possible, you can determine which model has the brightest "average" beam, thereby decreasing your chances of buying a lemon. Consistency between identical models by the same manufacturer would be good news for the prospective mail-order buyer, who doesn't get to test it before coughing-up the cash. Most of us don't get to buy our laser pointers over-the-counter. Certainly nobody going for the $35 special got to test it first. I'm betting that the more money you pay, the more identical are individual examples of the same model. If it's a waste of time to you, by all means don't participate, Guy. I'd like to borrow your laser pointer, though... ;o) --- diveboss@xmission.com wrote:
I don't know why a comparison of pointers needs to be such a big production. In choosing laser sights for weapons, you simply point the competing laser sights at a wall and go with the laser that produces the brightest and smallest spot.
Quoting Chuck Hards <chuckhards@yahoo.com>:
Make that "factor", not function.
Could be interesting, but we'd need a lot of distance between the laser operator and the person with the ruler. Also, a spot size small enough to measure directly would probably mean a hazardously bright environment directly in the beam. Kurt, you've researched lasers over relatively short distances, what do you think about this?
--- Chuck Hards <chuckhards@yahoo.com> wrote:
Don't you think that coherence will be a contributing function to brightness?
--- Michael Carnes <michaelcarnes@earthlink.net> wrote:
Seems like beam coherence (spread over distance) might also be a good thing to measure. That's the only thing that might require some space.
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Quoting Chuck Hards <chuckhards@yahoo.com>:
These things are usually used to point at infinity, and I bet your marksmanship isn't quite that good.
I can only hit a 5' target at 1163 yards with open sights, so yes, infinity would be beyond my marksmanship skills.
Wow, not even close! ;o) --- diveboss@xmission.com wrote:
I can only hit a 5' target at 1163 yards with open sights, so yes, infinity would be beyond my marksmanship skills.
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Actually, Guy is really quite right. This isn't a big deal. Even the dimmer green lasers I've seen are somewhat useful as pointers, the brighter ones work with more transparent air (higher altitudes, generally), although if the air is exceptionally clean even the brightest ones can be nearly invisible. More dust or water vapor in the air means a more visible beam. The brighter lasers are more visible when you get further off-axis, so larger crowds usually call for a bright laser. Something to consider if you are a lecturer at a large star-party. Light-pollution decreases the effectiveness of the laser. The darker the sky, the dimmer the laser you will find effective. Suburban skies will benefit from a bright laser. Something to consider for the person conducting school star-parties. It's mostly just an excuse to try and extract some data that may or may not be useful to a prospective purchaser. I thought it might be a cool way to spend an hour at a meeting on an otherwise moonlit or cloudy night, experimenting with a neat tool that we didn't have years ago. Seeing what the market offered, that's all. In practice it's really not a big production, anymore than any other club presentation with say, a slide projector. --- diveboss@xmission.com wrote:
I don't know why a comparison of pointers needs to be such a big production.
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They are even neater when used in the fog. Quoting Chuck Hards <chuckhards@yahoo.com>:
Actually, Guy is really quite right.
This isn't a big deal. Even the dimmer green lasers I've seen are somewhat useful as pointers, the brighter ones work with more transparent air (higher altitudes, generally), although if the air is exceptionally clean even the brightest ones can be nearly invisible.
More dust or water vapor in the air means a more visible beam.
The brighter lasers are more visible when you get further off-axis, so larger crowds usually call for a bright laser. Something to consider if you are a lecturer at a large star-party.
Light-pollution decreases the effectiveness of the laser. The darker the sky, the dimmer the laser you will find effective. Suburban skies will benefit from a bright laser. Something to consider for the person conducting school star-parties.
It's mostly just an excuse to try and extract some data that may or may not be useful to a prospective purchaser. I thought it might be a cool way to spend an hour at a meeting on an otherwise moonlit or cloudy night, experimenting with a neat tool that we didn't have years ago. Seeing what the market offered, that's all. In practice it's really not a big production, anymore than any other club presentation with say, a slide projector.
--- diveboss@xmission.com wrote:
I don't know why a comparison of pointers needs to be such a big production.
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I do, but consider the following;
Don't you think that coherence will be a contributing function to brightness?
A higher-powered laser with lower coherence might actually make a brighter spot at a short distance. But over a few thousand feet, you might get a better result with a little less power and better collimation. Having said that, I'd reiterate that we use these things to point out Sagitta (etc) at star parties. Anything that does the trick, does the trick. I think it would be a fun experiment, but not so much as a buying guide. I wouldn't expect anyone with a "losing" laser to have to throw it away. But it would be interesting to see how claims and prices stack up against reality. And remember, by the time February rolls around we'll be stir crazy. Anything that feels even remotely related to astronomy might be fun.
So we can go back to those 5-cell flashlights? Why did you tell me this AFTER I spent $100?? --- Michael Carnes <MichaelCarnes@earthlink.net> wrote:
Anything that does the trick, does the trick.
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participants (4)
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Michael Carnes -
Michael Carnes