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Clear skies to you

Pelagius

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Welcome SmallFreak! I love astronomical viewing!

AstroRB: K RB Astro
Fabulous shot! May I ask a few off the main topic questions? Do you use a tracker? How many shots did you stack?
I was reasearching trackers for Astro Photog when I stumbled into the Laser habit. Put off my purchase.
I'll follow up on the Astro thread. Thanks!!




Thanks fo the suggestions. I read some coments about the Laserlands 520nm 5mw pointer. That seem to be quite bright for the nominal values.

For astronomy use the 5mW range of the tested pointers was not quite enough to have a group of people around the astronomer have a good sight on the beam in a moonlit night. We had good experience with 20mW green pointers whereas 50mW were too bright in a dark night as it affects night adaption.

T

Yes.
They claim <1mW to get around the eBay rules, but everyone buying them knows that they are a lot more powerful, especially when they say they can burn matches etc.


Also, speaking of The Milky Way, just wanted to share a photo with you that I took out of my back yard.
I can only imagine how wonderful the Milky Way would look from your dark location.




Cheers
RB

:yh:
 



paul1598419

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There are actually a couple of telescope and astronomy threads here. They don't get posted to very often, so you might not have seen one yet.
 

Pelagius

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Hi Paul,
I'd not seen one. But then if they are old-responding would be "necroposting"-so I'm guessing its best to NOT.


There are actually a couple of telescope and astronomy threads here. They don't get posted to very often, so you might not have seen one yet.
 

BowtieGuy

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Hi Pelagius, some of those threads aren't that old, and besides, if you are posting with new information to add, it's generally not considered necroposting. :yh:
 

RB astro

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I think you could be right this time! :eek:
Oh, really?
Based on what?
Do you have access to any info, us moderators don't?

Please share.

RB

AstroRB: K RB Astro
Fabulous shot! May I ask a few off the main topic questions? Do you use a tracker? How many shots did you stack?
I was reasearching trackers for Astro Photog when I stumbled into the Laser habit. Put off my purchase.
I'll follow up on the Astro thread. Thanks!!
G'day Pelagius,
This was taken only with a Canon DSLR camera and 16mm lens on a tripod, no tracking.
I kept the sub frames short to minimise trailing, lens set to f/4, ISO 1600, (8) x 30 sec light frames, 4 min total.
I used a program called Registar to register, align and stack the images.

Also as Ears & Eggs said there's a telescope thread, and as Jeff (BowtieGuy) said, it's not considered necroposting if you have a comment and new info to add.

I'm at work atm but I might post some more LPF astro related links for you later.

Cheers
RB

:beer:
 

paul1598419

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As has already been stated, adding new information to one of these threads is not necro-posting. Regardless, if you are into astronomy you can certainly go have a look. That is why these threads still exist.
 

Benm

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Yes.
A nice little 505nm, 35mW would be ideal and you don't need to worry about the cold weather affecting the laser like a 532nm would.
Have a look at my build thread below.
I'd totally agree on that: get a direct diode pointer if you are concerned about IR safety. Since they produce the light you see directly there is no possible IR to leak out, and for your purposes they will be fine.

DPSS lasers are still superior in aspects like monochromaticity, coherence length, divergence/diameter ratios and such, but none of these properties a important if you just want to point at something in the sky.

How much power you need will vary a bit, but if 20 mW of 532 nm light worked well for you i'm sure that 30-40 mW of 505-510 nm will be at least as bright. Having the shorter wavelength may actually be beneficial for star pointing: Per mW the light is less bright to your eyes compared to 532 nm green, but on clear nights with unpolluted air you may depend on Rayleigh scattering to make the beam path visible, and since that gets more effective with lower wavelength (to the 4th power!) that may also help.

I'm not totally sure to what degree Rayleigh scattering makes a laser beam visible though, i live in an urban environment where fine dust is probably the main factor making laser beams visible (red, green and blue look about as bright per mW as for the visual response curve).
 

paul1598419

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If you are going to use this to point out stars, you won't be using goggles to do that anyway. Why spend a lot of money to get the direct diode when the 303 532nm lasers are so very inexpensive? The beams are better looking too.
 

kecked

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If you want a lot of posts try cloudynights.com. All about Astro

Welcome. Is that mars I see in that image?
Amazon sells three points for 5.00. Rgv. Poorly made but they work.
Please checkout Laser Pointer Safety - A comprehensive resource, for safe and responsible laser use in regards to pointing at the sky.
He is USA it’s a big deal. Maybe not where you are.

A green laser 5mw 1mRad div is a distraction to pilots 2 miles away.
20mw is 5miles
100mw 10 miles and then you are into flash blindness at 1mile
If you can do 5mw it makes sense.

Here is the eye hazard data for same. This means you only have a 50%chance something bad will happen if the beam sweeps over your eye for 0.25s. This does not mean stating into the beam and it is only for the visible not Ir.

5mw 52’
20mw 104’
100mw 234’

End point be safe have fun. Used responsibly it’s all good. Never ever point at airplane.

https://www.amazon.com/pieces-Laser-Torch-Style-Fixed/dp/B07BQDSKQ7/ref=sr_1_10?ie=UTF8&qid=1534434802&sr=8-10&keywords=laser+pointer
 
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paul1598419

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I totally disagree that flash blindness will occur at 1 mile with a 100 mW 532nm laser. Try it some time. Even at a divergence of 1 mrad, the beam profile is spread out so much that you can look directly at it without seeing much more than a green light. Some of these stats are completely false and are there to scare people who don't know any better. You would also never have the beam on anything a mile away for more than a tiny fraction of a second.
 

smallfreak

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Please checkout Laser Pointer Safety - A comprehensive resource, for safe and responsible laser use in regards to pointing at the sky.
He is USA it’s a big deal. Maybe not where you are.
...
If you can do 5mw it makes sense.
Thanks for the link. While I cannot imagine what kind of people are pointing a laser at some living creature/plane/helicopter I'm not one of them. None of the astronomers I know would be that silly to intentionally shoot at a plane. :banghead:

Not primarely because it might disturb the pilot, but rather because of common sense. You WILL face troubles and you cannot hide, as a laser beam has two ends. It is quite easy to spot where the idiot is located - precisely at the down end of the beam.

In Austria everything is a bit smaller than in the US. So are the regulations and fines. >5mW IS prohibited here unless you got a special permission for a certain use. Astronomers got a dispense from this regulation. Star pointing during a public observing session by "trained people" currently is tolerated. We try to give the authorities no reason to rethink this.

But you will not get locked up to prison for the rest of your life for "violating the law". It truly depends on the actual harm done.

If you blind a pilot and he turns back home, the company and passengers have a lot of expenses. If they get hold on you, this might get VERY expensive.

These "jokes" don't seem to be much of a problem here. There is almost no public focus on it - and the papers would certainly make a headline of such a case. Maybe we have not that much pointers circulating, maybe our people do not find it that funny, maybe they are not as goony as we sometimes think about how "the americans" must be when we read certain "american safety instructions for idiots". Common sense is still very strong in Europe. I hope you don't get me wrong on this. I know that this results from the US legal system not because they would be more stupid than other people.
:beer:

The dangers at a star party are various.
  • You get a bump from a passing guest while pointing at something
  • your cold finger loose grip
  • waving the hand you may hit something reflecting
  • you might get tempted to grant the wish "may I just show you something" and hand the pointer over to some untrained person.
  • ...
The problems multiply with a ponter that might be switched on permanently.

Unfortunately(?) we usually have very clean and mostly dry air, where you will have a hard time to show the stars with a 5mW pointer, even a green one. It IS possible, if you just have 2 or 3 people directly beside you. Then even a 5mW red pointer might be enough in a moonless night.

If you have to show it to a crowd, 10mW are acceptable, 20mW are good. More is nice to have. 50mW is BOAH! but does not give a distinct benefit for the intended use. So if the cheap pointer really exceed that range, I will have to dim it.
 

Benm

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Let's be a bit realistic here about any danger to aircraft:

As you're doing astronomy to begin with, you'll be looking at the sky to begin with, and probably not in overcast conditions either.

Any (commercial) aircraft flying below 10.000 feet are required to have their strobe lights on (those white and red flashing lights on the wings, top and bottom), so if you're standing outside at night these will be -very- visible to you (heck, they're visible from inside my living room with the lights on when i look outside at night), and you should not point lasers at them, not even 1 or 5 mW ones either.

The chance if doing any permanent eye damage to pilots or passengers is basically zero, but it could still distract them, and in extreme cases perhaps cause some flash blindness that would hinder them when doing a visual approach looking for the runway, papi lights etc.

As far as planes at cruise altitude go: they should not be affected by someting like a 50 mW laser pointer really - due to divergence the light from that laser is spread over an area about as large as the whole plane so it's not very intense.

So if an aircraft with it's strobes on flies into your field of view, stop using the laser. If you cannot see it it'll probably be at cruise altitude with most lights off (usually only wingtip and white steady beacons on, hardly visible from the ground).

If planes fly at low altitude without their strobes on the fault is also on part of the pilot: the rule is 'see and be seen'. Something like that could happen due to technical failure (loss of all electrical systems) but that'd be extremely rare, it doesn't rain airplanes right?
 

paul1598419

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Also, the difference between a 50 mW 532nm laser and an 80 mW one, visually, is not something you will be able to see. The 30 mW difference doesn't mean it is that much brighter because your eyes aren't linear in the way they see brightness. So, again, the $10.00 303 532nm laser you can buy with a battery and charger will basically look like a 50 mW green laser regardless of its actual power. The most these ever put out is really only maybe 90 mW. But, your chances of getting one of these is quite small. If you measured it with a calibrated laser power meter it might fall in the 50 mW to 70 mW range, but both would look equally bright.
 

kecked

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That’s all based on physics well backed up in the literature. I just ran the calculations based on what the law says. Argue with Cdrh and Congress. Your opinion so noted.

The studies I used are based on real measurements in humans and animals where damage occurred. It’s all based on accidental exposure less than 0.25s which is based on the blink response of a human.

Flashblindness is based on the saturation of the rods and cones and the amount of time to recycle. Distraction is I agree is subjective as is glare. Is the win shield dirty?.....

So some of it is opinion but the NOHD and ED50 are measured toxicology. I can post the math if required. Just took my laser safety officer training last week so it’s very fresh.

I agree chances of eye damage are nil in a plane except landing and take off and you need a power full couple watt laser.

A beam with 1 mRad at 1000m starting at 1mm is 1m in diameter by definition. So say 3000 feet. At 30,000 feet the beam would be 30’or so in diameter.

Distraction or glare in the critical phase of flight is the most dangerous. As said just avoid the planes. I gave the nominal eye damage distances for the people on the ground as you mentioned fear about it.
 
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paul1598419

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A green laser 5mw 1mRad div is a distraction to pilots 2 miles away.
20mw is 5miles
100mw 10 miles and then you are into flash blindness at 1mile
If you can do 5mw it makes sense.

Here is the eye hazard data for same. This means you only have a 50%chance something bad will happen if the beam sweeps over your eye for 0.25s. This does not mean stating into the beam and it is only for the visible not Ir.

5mw 52’
20mw 104’
100mw 234’
[/url]
I don't know where you got these stats, but almost everyone who has been here for a long time knows that a green 5 mW laser might not even be seen at all a mile away, much less two miles. I have seen similar stats posted before you posted these, but your source is NG. If you did the math, you would see as much too.

That’s all based on physics well backed up in the literature. I just ran the calculations based on what the law says. Argue with Cdrh and Congress. Your opinion so noted.

The studies I used are based on real measurements in humans and animals where damage occurred. It’s all based on accidental exposure less than 0.25s which is based on the blink response of a human.

Flashblindness is based on the saturation of the rods and cones and the amount of time to recycle. Distraction is I agree is subjective as is glare. Is the win shield dirty?.....

So some of it is opinion but the NOHD and ED50 are measured toxicology. I can post the math if required. Just took my laser safety officer training last week so it’s very fresh.

I agree chances of eye damage are nil in a plane except landing and take off and you need a power full couple watt laser.

A beam with 1 mRad at 1000m starting at 1mm is 1m in diameter by definition. So say 3000 feet. At 30,000 feet the beam would be 30’or so in diameter.

Distraction or glare in the critical phase of flight is the most dangerous. As said just avoid the planes. I gave the nominal eye damage distances for the people on the ground as you mentioned fear about it.
If you insist this is all correct, I would like to see the link to this information. A 1 mrad green laser is not the norm. You are more likely to get a 1.5 mrad instead. So, at a 1000m even a 100 mW laser will not even cause flash blindness. And the IR component of an unfiltered 532nm laser at 1000m is not even worth talking about. It will diverge much more quickly and at worst is ~20% of the total power.
 




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