Star pointing

[Bakawun]

Hi all,
I'm getting an o-like green module to use in a custom Maglite build I've been working on with Jayrob (mad props, the man is a genius with lasers). At any rate I'm going to be using the laser solely for star pointing, and I was wondering what output I should get. Anyone know what would be best?

Thanks, Baka

 

[Emc2]

Hi all,
I'm getting an o-like green module to use in a custom Maglite build I've been working on with Jayrob (mad props, the man is a genius with lasers). At any rate I'm going to be using the laser solely for star pointing, and I was wondering what output I should get. Anyone know what would be best?

Thanks, Baka

Sure I can help. What size crowds will you be entertaining? A 20mW is a nice power for star pointing, use a 50mW if you will be pointing to the stars from hevily light polluted skies so the crowd can see the beam. Astronomy is a long tome hobby of mine and I have used various powers and a 20~50mW will be sufficient. But like I said, it all depends on the crowd size and sky conditions.

-Todd

 

[Elektrotechniker]

I suggest you use a 50 mW module Its beam is more visible than 20mW.

 

[scopeguy20]

I actually use several, I like a 15 mW for use on the scope when I want to visually see the dimmest possible target naked eye. I saw a 6.6 magnitude asteroid from my suburban backyard where the Milky Way is often a challenge to see. I think knowing exactly where to look extends the ability to see, but my 50 mW would have diminishes my night vision for that viewing. I do show others the 50 mW and they are often more interested in the laser than the stars, and once in a while I point them out with my 300 mW red laser or my 10 mW blue laser, just to mix it up. Violet scatters so that te beam will look sort of fat at long range and disappears at a shorter distance, so it and blue are not as good for star pointing. I would recommend for all around use, a 30 mW, it is a pretty good choice in a green laser with just a few people watching.

Here are some lasers in the fog at night. In this view the beams are seen for under 50 feet as they terminate on the bushes near my back fence.
-Glenn

 

[Bakawun]

Thanks everyone!
Since I'll be using it with varying scenarios (small groups up in the mountains, far from any light pollution VERSUS in towns with groups of 20 or more), I might get a 15, and a 50, and just make two builds.

I really appreciate all the responses (and that beam shot of the 6 lasers is SWEET )!

I was considering a 100mW but that seems like a bad idea. So now it's just a matter of whether or not to go with a 50 and/or a 15.

Will the divergence on higher outputs cause trouble, or will I still get a good narrow beam even with more power? I mean refraction in humidity or smog could cause trouble as the output goes up, no?

Thanks, Baka

 

[Deleted member 8382]

Thanks everyone!
Since I'll be using it with varying scenarios (small groups up in the mountains, far from any light pollution VERSUS in towns with groups of 20 or more), I might get a 15, and a 50, and just make two builds.

I really appreciate all the responses (and that beam shot of the 6 lasers is SWEET )!

I was considering a 100mW but that seems like a bad idea. So now it's just a matter of whether or not to go with a 50 and/or a 15.

Will the divergence on higher outputs cause trouble, or will I still get a good narrow beam even with more power? I mean refraction in humidity or smog could cause trouble as the output goes up, no?

Thanks, Baka

Consider taking a true 50mW from dealextreme, it's more than enough for a unbeateableprice.

yours,
Albert

 

[Jazlikethat]

If you live in the US, like me, and Deal Extreme doesn't ship to you, you can try this one.

http://www.budgetgadgets.com/keychain-green-beam-laser-pointer-flashlight-30mw50mw-p-3939.html

I'm a noob and this is my first laser I got it a week ago and I'm loving it. Great price great quality. There's a review on it in the review section. The only problem is if you're point at dim stars/satellites sometime they'll disappear for a second as your eyes readjust. This has only happened to my once though, on the dimmest satellite I have ever seen.

 

[Darkarmyofone]

... i cant see any satalites in the sky... are you all seeing these things naked eye? or shining a laser at it then looking through a scope of some sort to actualy see the satalite?...

and something i've ALWAYS wondered.. does a high power laser...say 1watt green STOP at any point? i mean does the beam go "forever" even through space, or will it dissapate before then..... thinking on it now... you could probably never get a beam focused so perfectly tight to infinity that it would just get way too wide way before it even reaches the stratosphere "or w/e the bottom layer is"

always wanted to ask that question, and never had a good place to ask it, but the stargazing talk makes me want to pick up the hobby again.

i actually know a guy who saw some discovery show about how they shoot lasers at that reflective thing appolo 13 left on the moon, and the laser bounces back and they can judge the distance of the moon that way. he seems to think this is feasable to reproduce on a "residential backyard" scale. but i beg to differ i guess... the laser on that show was in the thousands of watts i do beleive... oh yeah and it was the size of an entire telescope lab thing "those white domes they use to house MASSIVE telescopes" yeah it was in one of them things.... WAY too big... and 1000watts... god what kind of power/current would one need to provide to acheive that...

it'd be great if they could make all that into a nice 5.6 mm diode LMAO, maybe when pigs fly...

anyways any thoughts about by beam travel question are very welcome.

Dark

 

[chipdouglas]

i've noticed that all my greens seem to go the same vertical distance. Some body explained it as atmospheric particles not being abundant at a certain level which would make sense. but recently I pointed my dilda and my green side by side straight up and the red seemed to go higher. pretty weird.

 

[scopeguy20]

Darkarmyofone, I too have noticed that the visible beam is wavelength related. I have a 300 mW red about 660 nm, and see it going about 5% or so further than my green ones, also my violet looks about 70% as long or less. I believe there are three factors, the shorter wl will scatter much more leaving less intensity to go on illuminating the medium, there is much drier and lower dust air in the higher elevations, and the inverse square law shows that something twice as far and as bright will look 1/4th as bright, so as the beam gets far enough out, it suffers the combination of these, and the most scatter loss in the shorter Wl's hence blue looking sky in day and red looking sun at a sunset. -Glenn

 

[Darkarmyofone]

interesting information, so then TECHNICLY red, and IR "even though IR is useless to the NAKED eye" is the best choice for stargazing if your depending on a long beam...dont know why you would but i guess its red for length/distance and green for sheer visibility

 

[LinkC]

I use a cheapie 5mW piggy-backed on my scope finder for rough pointing. Since I'm looking straight up the beam, it's clearly visible.

For crowds, I use a 22mW. There's no need for more than that. Last month I did a program for 138 people at a Nature Festival. Some had a hard time hearing me, but NO one complained that they couldn't see the laser.

A brighter beam in either of those usages would only reduce dark-adaptation. Have some consideration for your audience.

 

[willpine]

would yall say the typical 1 watt 445 beam would be visible to about 750 ft or so, pointed up on a clear night?
and similar for a 150 mW green?
and for why? is the best explanation b/c basically density of particles in higher atmosphere? it wouldnt seem that different only that high up..

thanks for any comments, i was wondering this question and knew somebody asked a similar question but ive been looking for an hour and this is the best ive found so far

 

[david1235102]

if you use more than a 50mW green then you will probably have more people looking at the beam rather than the star the beam is leading to or, at least i would be.

 

[scopeguy20]

Green and Blue look a mile or two long in the night sky... the longer the wl the more it penetrates, so, a violet beam that looks easy to see, (400+ mW) will look shorter than a blue 445-447nm or 473nm, which will be shorter than a green 532nm, the red will have trouble being seen to be much longer, as red is hard to see as it gets dim, and we rarely see a red over 290mW -GH