Lowest output but still Hi-WOW for nitesky?

[JBTexas]

Soon, I THINK I want to do my first DIY laser (green). I have browsed thru the manufacturers, and the DIY / Guide threads on these forums. I still have decisions to make and questions to ask (what host, which battery chemistry, etc?)... and I need to finalize my list of questions, all of my requirements, etc.

In the meantime, here is one thing that should be relatively easy to answer.

I lack the practical experience.

What is a good (minimum) output for a "highly night-sky visible" green portable laser (assume it will be a DIY, probably from one of the kits in these forums)?

I am NOT really interested in burning things. BUT I would like a laser that, when pointed up into the sky, will be very visible, even when NOT at a low angle of incidence... I.E. so that spectators, from, say, across a parking lot could see it when aimed at the zenith? MINIMUM power required to do that... if it ends up as a burning laser, fine.

I am guessing about 50 - 100 mw?

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Rest assured, my FIRST purchase before ANY of the parts WILL be safety goggles. As far as I can tell, rule of thumb = make sure the goggles can reduce/filter the power down to <= 5 mw (probably less)? I have a conversion chart-thing that I downloaded from somewhere, to help calculate necessary OD. (recommendations of "best/safest" source? Which goggles to "stay away from"?)

EDIT

Just in case it comes up...
I have been a radio amateur since the mid '80s. I got stuff. Soldering stuff.

 

[Trevor]

You're going to need far more optical power than 50-100mW.

To be able to see a beam at 90 degrees from 100+ feet away... I'd say you're looking at a baseline class IV device.

-Trevor

 

[JBTexas]

Trevor;

Thanks... all I have to go on are YouTube videos and pics here in the forum.

Any somewhat-specific reasonable opinions would be appreciated.

Ok, not ... say ... 90 degrees from 100 feet away... hmmm... but say larger than a typical star party gathering. Say, from across a highway then.

I just don't want to waste effort... wanna make it right the first time.

(maybe I WILL need to go quite a bit higher??)

 

[Trevor]

Hm, I'll go outside with my 200mW green handheld tonight and see how far away I can see it when it's directed straight up.

My main points of reference are my old 150mW pointer )which faded away quickly as you moved away from it) and my 1.5W green lab system (which you couldn't help but see, from a significant distance).

-Trevor

 

[JBTexas]

Thanks, Trevor. That really would be informative... if "visibility" is a factor, then if you could do that it would give me a clearer picture of what I want / what I am trying to do.

 

[Trevor]

Well, I went out and tested it last night. From about 150' away, the beam was getting really faint.

It was rather humid outside and the beam on this laser is also thicker than most.

So for trying to impress far-off people, you're going to need that amount of power or more.

-Trevor

 

[HIMNL9]

Also, remember that beam visibility is matter of how much dirt-dust-mist there is suspended in the air ..... 100mW in a mist / foggy night can be much more "visible" than 1W in a perfectly clear air night .....

 

[Trevor]

Also, remember that beam visibility is matter of how much dirt-dust-mist there is suspended in the air ..... 100mW in a mist / foggy night can be much more "visible" than 1W in a perfectly clear air night .....

This is true; that's why I mentioned humidity. If it's consistently humid in Texas, then you might be able to get away with less power.

I was once in a really rural area and fired up my 1.5W green on a foggy night. So much win.

-Trevor

 

[JBTexas]

Trevor;

Thanks a lot for doing this. I appreciate it. So, say, up to 50-75-100 feet or so = people will see it ok, and maybe more. Probably.

Humidity: Here in Abilene Texas it is kind of dry... as a matter of fact it looks like we are heading into the usual summer drought (after all of the recent tornados... I live at the SW tip of "Tornado Alley"). When it DOES rain here, it does so violently - with lots of voltage.

BUT what we DO have is DUST and LOTZ of it! Once a week I have to vacuum a virtual potato farm out of my computer. (just exaggerating - no potatoes)

My new green 5mw LaserGlow Lyra B-5 pen shows up fairly well outside at night. Perpendicular / 90 degrees to beam = JUST visible. Low angle of incidence = very visible (for 5 mw). With my arm stretched way out (to the side) and pointing at the sky = "still visible but faint".

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DIY:
OK - over the past few days I have been collecting info from the Tutorials, BuySellTrade, Laser Pro Shop, Deals and Discounts.

I've been a Radio Amateur since the mid 80s, I can solder. BUT I have no/little experience with optics, or machining. I have better than average soldering supplies, an "average" set of tools incl. miniature screwdrivers and allen wrenches, etc...

I have NO machining tools. I DO NOT have a glue gun.

The info I have collected is... intimidating. SO I have decided NOT to do a DIY project, for now. Maybe later. I LIKE several of the host kits offered here... mainly for their solidness, and probable heatsinking abilities.

So I JUST ordered this from O-like a few minutes ago (pasted from my email receipt):

Products
------------------------------------------------------
1 x universal Tripod for laser torch/dia from 16-44mm (OL-T-1644) = $12.99
1 x CR123A Charger with battery (OLCH) = $7.00
1 x New Gatlin Green laser 200mW/waterproof/adjustable (OLGA-200) = $189.00
------------------------------------------------------
Sub-Total: $208.99
Flat Rate (Best Way): $8.00
Total: $216.99

I hope I will be pleased. That Gatlin LOOKS like it should disperse heat pretty well. I have no idea what the duty cycle will be (isn't posted on the O-Like website), but if it isn't in a spec sheet when it arrives, I will assume the usual 60-90 seconds plus maybe 30 seconds for cooling... although I have found posts that say that the duty cycle is usually exaggerated, and some people run their 532's for several minutes with no problems.

Also, I have sent a PM to Garoq / Survival Lasers about ordering Eagle Pair goggles. (something on his website I wasn't sure of - minor issue)

 

[Helios]

As has been said its all about whats in the air. Remember that the beam IS NOT visible. The laser light reflecting off of particles and such in the way of the beam is visible. In a vacuum with no particles no amount of laser power would have a visible beam.

200mW should be very visible for you the operator and could be visible for others as well depending on conditions but it will change from one night to the next to some degree.

Be careful. 200mW is great for sky pointing but lookout indoors and grab those glasses asap. Also look IR leakage of DPSS pointers because even most safety glasses wont protect you from that. I have metered green lasers that put out 30mW IR THROUGH green reflect goggles!