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Main
Date: 05 Aug 2007 16:41:13
From: beowulf@nowhere.net
Subject: pocket lasers for star pointing?
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Before I buy a telescope, I want to get out and learn basic
constellations, etc, naked eye and binoculars. But I see in magazines
there little pocket lasers for pointing up in the sky. Are they really
worth it, useful? They are priced by wattage, what sort of wattage is
typically needed? I see 35mw models for $170, 125mw models for $550.
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Date: 06 Aug 2007 21:13:33
From:
Subject: Re: pocket lasers for star pointing?
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I've been looking at laser pointers on Ebay and notice that the green
ones (which I believe are better for astronomy) are much more
expensive. Red ones are literally a few dollars, green ones are tens
of dollars.
Is this because there is a shortage of supply of green, or are green
actually more expensive to make?
Barry
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Date: 07 Aug 2007 04:23:23
From: David Nakamoto
Subject: Re: pocket lasers for star pointing?
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barryh46au@yahoo.com.au wrote:
> I've been looking at laser pointers on Ebay and notice that the green
> ones (which I believe are better for astronomy) are much more
> expensive. Red ones are literally a few dollars, green ones are tens
> of dollars.
> Is this because there is a shortage of supply of green, or are green
> actually more expensive to make?
> Barry
More expensive to make. It takes more energy to produce the higher
frequency green photons, so it take more to make the laser, roughly
speaking.
--- Dave
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Date: 07 Aug 2007 04:20:54
From: Skywise
Subject: Re: pocket lasers for star pointing?
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barryh46au@yahoo.com.au wrote in news:1186460013.052615.108960
@j4g2000prf.googlegroups.com:
> I've been looking at laser pointers on Ebay and notice that the green
> ones (which I believe are better for astronomy) are much more
> expensive. Red ones are literally a few dollars, green ones are tens
> of dollars.
> Is this because there is a shortage of supply of green, or are green
> actually more expensive to make?
> Barry
Red can be done with cheap mass produced direct injection diodes.
If you know what an LED is, it's basically a fancy version of that.
And it emits the color directly, typically 680nm to 635nm
Green is more complex. It starts with an IR diode at 808nm. This
excites a crystal of Nd:YVO4 which then lases at 1064nm. This is
then frequency doubled with a crystal of KTP, which converts it
to the 532nm green. Needless to say, this is much more complex.
The crystals aren't cheap to make, have to be cut and polished in
a precise angle relative to the crystal lattice, are coated with a
combination of anti-reflection and high reflection coatings for
the various wavelengths, and all have to be aligned properly. Also,
due to power losses at each conversion step, the 808nm diode is
typically half watt of power or more, which cost a bit more.
When green laser pointers first came out, they cost a grand or more.
Brian
--
http://www.skywise711.com - Lasers, Seismology, Astronomy, Skepticism
Seismic FAQ: http://www.skywise711.com/SeismicFAQ/SeismicFAQ.html
Quake "predictions": http://www.skywise711.com/quakes/EQDB/index.html
Sed quis custodiet ipsos Custodes?
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Date: 07 Aug 2007 01:06:10
From: Skywise
Subject: Re: pocket lasers for star pointing?
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"beowulf@nowhere.net" <r.oelerich@gmail.com > wrote in
news:1186332073.164866.140840@i13g2000prf.googlegroups.com:
> Before I buy a telescope, I want to get out and learn basic
> constellations, etc, naked eye and binoculars. But I see in magazines
> there little pocket lasers for pointing up in the sky. Are they really
> worth it, useful? They are priced by wattage, what sort of wattage is
> typically needed? I see 35mw models for $170, 125mw models for $550.
I just ran across this thread and have some things to point out...
Speaking for US law...
A "laser pointer" must be less than 5 mW.
ANY laser operated in public or out in the open (ie unterminated
beams pointing in the sky) over this power limit without a variance
is illegal and could, theoretically, land you in varying degrees
of hot water.
Cheap laser pointers CAN leak sufficient levels of IR light to be
an eye hazard.
Even a legal laser of low power can be dangerous. Even if no
actual physical damage is caused, the dazzle effect can be
quite dangerous, especially to the night adapted eye in a dark
place - such as an aircraft flying at night.
I see those same ads in the astro mags and certain ones I have
written in complaints regarding them numerous times because the
products they are selling ARE illegal. Period.
Not all the laser pointers advertised are illegal, though.
But beware of ads for stuff shipped from over seas. Customs has
been confiscating items. You could lose your new toy and your
money.
Although lasers can be a lot of fun, they are NOT toys.
Brian
--
http://www.skywise711.com - Lasers, Seismology, Astronomy, Skepticism
Seismic FAQ: http://www.skywise711.com/SeismicFAQ/SeismicFAQ.html
Quake "predictions": http://www.skywise711.com/quakes/EQDB/index.html
Sed quis custodiet ipsos Custodes?
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Date: 06 Aug 2007 20:52:33
From: Chris L Peterson
Subject: Re: pocket lasers for star pointing?
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On Tue, 07 Aug 2007 01:06:10 -0000, Skywise <into@oblivion.nothing.com >
wrote:
>Speaking for US law...
>
>A "laser pointer" must be less than 5 mW.
But a "laser pointer" can be legally modified to output more than 5mW,
as long as it is properly labeled (doesn't still carry its class 3a
sticker).
>Cheap laser pointers CAN leak sufficient levels of IR light to be
>an eye hazard.
I don't think this can easily happen- especially with the cheapest
models. I know of no case of it actually happening.
>Even a legal laser of low power can be dangerous. Even if no
>actual physical damage is caused, the dazzle effect can be
>quite dangerous, especially to the night adapted eye in a dark
>place - such as an aircraft flying at night.
The airplane example is a crock. There's no way a 5mW laser is capable
of dazzling a pilot flying at any reasonable altitude. Of course, if you
stand on the end of a runway you might be able to manage it, but that's
not a realistic scenario.
>I see those same ads in the astro mags and certain ones I have
>written in complaints regarding them numerous times because the
>products they are selling ARE illegal. Period.
How so? Are they being sold as class 3a devices? I'm not doubting you,
just wondering what criteria you see which makes some legal and some
illegal.
_________________________________________________
Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com
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Date: 07 Aug 2007 04:40:44
From: Skywise
Subject: Re: pocket lasers for star pointing?
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Chris L Peterson <clp@alumni.caltech.edu > wrote in
news:i8nfb3t085eamg1gmtameds44tq6u39fhs@4ax.com:
> On Tue, 07 Aug 2007 01:06:10 -0000, Skywise <into@oblivion.nothing.com>
> wrote:
>
>>Speaking for US law...
>>
>>A "laser pointer" must be less than 5 mW.
>
> But a "laser pointer" can be legally modified to output more than 5mW,
> as long as it is properly labeled (doesn't still carry its class 3a
> sticker).
Sure, you can modify it all you want. But don't sell it or use
it in public or you're breaking the law.
>>Cheap laser pointers CAN leak sufficient levels of IR light to be
>>an eye hazard.
>
> I don't think this can easily happen- especially with the cheapest
> models. I know of no case of it actually happening.
It can and does. There are many pointer modders out there who
actually remove the IR blocking filters, or due to the cheap
design, when it's modded it emits more IR. This has been
verified by those who have laser power meters buying a pointer
claimed to be 50mW and finding it's maybe 10 to 15mW of green
and several tens of mW or leaking IR. Under these circumstances
a power meter calibrated for green will indicate and erroneous
high power reading due to the leaking IR. It's a known scam
amongst us laser hobbyists.
>>Even a legal laser of low power can be dangerous. Even if no
>>actual physical damage is caused, the dazzle effect can be
>>quite dangerous, especially to the night adapted eye in a dark
>>place - such as an aircraft flying at night.
>
> The airplane example is a crock. There's no way a 5mW laser is capable
> of dazzling a pilot flying at any reasonable altitude. Of course, if you
> stand on the end of a runway you might be able to manage it, but that's
> not a realistic scenario.
I dare you to try it.
The only caveat is the difficulty of actually hitting the pilot
in the eye. But if you manage to do it, it's certainly going to
be dazzling.
At any rate, it's not a good idea to try.
One last thing, I am specifically talking about dazzling one's
vision, not causing any sort of damage.
>>I see those same ads in the astro mags and certain ones I have
>>written in complaints regarding them numerous times because the
>>products they are selling ARE illegal. Period.
>
> How so? Are they being sold as class 3a devices? I'm not doubting you,
> just wondering what criteria you see which makes some legal and some
> illegal.
A laser point has a simple on/off switch. This is allowed for
devices under 5mW of power. Above that, if the laser device is
being used in a public setting, as opposed to a controlled lab,
or incorporated in another device that prevents exposure, the
laser is required to have a minimal power on delay, an emission
indicator (laser on light), and a key switch for safety.
A modded laser pointer does not have these.
There are some folks out there who are making "hand held lasers"
which have these safety features, but there are also other laws
which some of these manufacturers are skipping out on. As a
manufacturer, they are required to maintain certain paperwork
and make certain reports to the CDRH.
Oh, and modding a laser pointer for resale purposes technically
makes you a manufacturer.
I've been an active laser hobbyist for at least 10 years. I've
got some knowledge of these things, either learned on my own or
passed on by laser show professionals in the biz for decades. A
few did tours with some great bands going back to the 70's.
But please don't just take my word for it. Here's some reference
material for you, all on the FDA's web site.
"Important Information for Laser Pointer Manufacturers"
http://www.fda.gov/cdrh/radhealth/products/lpm.html
"Illuminating Facts About Laser Pointers"
http://www.fda.gov/fdac/features/2005/305_laser.html
"IMPORT ALERT #95-04"
http://www.fda.gov/ora/fiars/ora_import_ia9504.html
And finally, the legal code regarding lasers,
http://www.accessdata.fda.gov/scripts/cdrh/cfdocs/cfcfr/CFRSearch.cfm?FR=
1040.10
If you want to learn more about lasers, there's the alt.lasers
newsgroup. A massive source of information is the LaserFAQ, to
which I have made very minor contributions. This can be found at
http://www.repairfaq.org/sam/lasersam.htm
Brian
--
http://www.skywise711.com - Lasers, Seismology, Astronomy, Skepticism
Seismic FAQ: http://www.skywise711.com/SeismicFAQ/SeismicFAQ.html
Quake "predictions": http://www.skywise711.com/quakes/EQDB/index.html
Sed quis custodiet ipsos Custodes?
|
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Date: 06 Aug 2007 22:58:20
From: Chris L Peterson
Subject: Re: pocket lasers for star pointing?
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On Tue, 07 Aug 2007 04:40:44 -0000, Skywise <into@oblivion.nothing.com >
wrote:
>Sure, you can modify it all you want. But don't sell it or use
>it in public or you're breaking the law.
It is legal to modify it for more power and sell it, as long as it's
labeled properly. There are no general restrictions on laser power in
the U.S. And you can use a higher power laser in public, depending on
the circumstances. The requirement for variances for indoor use depends
on jurisdiction. It appears that much of the federal regulation (such as
FDA) depends on intent and advertising. If you don't call it a pointer,
you may be okay.
>It can and does. There are many pointer modders out there who
>actually remove the IR blocking filters, or due to the cheap
>design, when it's modded it emits more IR.
But it still isn't very much total power, and it isn't well collimated.
The point is, it isn't likely to be dangerous.
>I dare you to try it.
Not a chance. Not while the U.S. is a police state. That doesn't change
the fact that it's far easier to dazzle a pilot with a halogen spotlight
than a laser, but nobody seems to worry much about that. There's a lot
of laser paranoia.
>"Important Information for Laser Pointer Manufacturers"
>http://www.fda.gov/cdrh/radhealth/products/lpm.html
Thanks for the references. The FDA wasn't involved in this in any way
back when I was a laser safety officer at Beckman Instruments in the
80's.
_________________________________________________
Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com
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Date: 07 Aug 2007 05:59:44
From: Skywise
Subject: Re: pocket lasers for star pointing?
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Chris L Peterson <clp@alumni.caltech.edu > wrote in
news:4aufb3p5798jtdk72aasmh4gocurasc645@4ax.com:
> On Tue, 07 Aug 2007 04:40:44 -0000, Skywise <into@oblivion.nothing.com>
> wrote:
>
>>Sure, you can modify it all you want. But don't sell it or use
>>it in public or you're breaking the law.
>
> It is legal to modify it for more power and sell it, as long as it's
> labeled properly. There are no general restrictions on laser power in
> the U.S. And you can use a higher power laser in public, depending on
> the circumstances. The requirement for variances for indoor use depends
> on jurisdiction. It appears that much of the federal regulation (such as
> FDA) depends on intent and advertising. If you don't call it a pointer,
> you may be okay.
Outdoor also requires a variance and now you'll also have to get
FAA approval. Location has nothing to do with it. Power level is
the determining factor here.
This subject comes up regularly in alt.lasers.
>>It can and does. There are many pointer modders out there who
>>actually remove the IR blocking filters, or due to the cheap
>>design, when it's modded it emits more IR.
>
> But it still isn't very much total power, and it isn't well collimated.
> The point is, it isn't likely to be dangerous.
Depends on the circumstances. Why take a chance? Especially
with something that's invisible. In the hands of someone who
is experienced and knowledgeable with lasers and their dangers,
it's probably just fine. But we're talking about your typical
Joe Blow public person here. You know, the type that likes to
talk on the cell phone while driving?
>>I dare you to try it.
>
> Not a chance. Not while the U.S. is a police state. That doesn't change
> the fact that it's far easier to dazzle a pilot with a halogen spotlight
> than a laser, but nobody seems to worry much about that. There's a lot
> of laser paranoia.
Yes, there is a lot of laser paranoia. There have been many
media reports of "eye damage" to pilots from lasers. And that's
all it's been, reports by sensationalist smoke blowing talking
heads.
I've done the calculations that show even a 50 watt laser would
have a hard time causing retinal damage even at thousands of
feet.
Sure, a 5mW green laser pointer won't cause damage, and might not
even dazzle except under the right circumstances. But that still
doesn't make it OK to do. Police state or not.
>>"Important Information for Laser Pointer Manufacturers"
>>http://www.fda.gov/cdrh/radhealth/products/lpm.html
>
> Thanks for the references. The FDA wasn't involved in this in any way
> back when I was a laser safety officer at Beckman Instruments in the
> 80's.
What's important is what the law is now.
The only reason I make a fuss over this is I am trying to
protect my hobby from the filthy paws of the government.
There's enough regulation as it is and I don't want any
more because of idiots doing stupid shit with lasers
drawing the wrong kind of attention.
I invite you to go over to alt.lasers and pose your questions.
There's folks there far more knowledgeable and experienced
than I.
Brian
--
http://www.skywise711.com - Lasers, Seismology, Astronomy, Skepticism
Seismic FAQ: http://www.skywise711.com/SeismicFAQ/SeismicFAQ.html
Quake "predictions": http://www.skywise711.com/quakes/EQDB/index.html
Sed quis custodiet ipsos Custodes?
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Date: 06 Aug 2007 08:44:05
From: callisto
Subject: Re: pocket lasers for star pointing?
|
Green laser pointers can cause eye damage as pointed out above.
However, it is unlikely to do so because when the eye sees the light,
there is a tendency to immediately look away. As the Mayo Clinic
study of 2005 stated:
"This is a potential hazard to people's eyes, but rarely is it going
to be a practical hazard because the aversion reflex we have naturally
will cause a person to blink or turn away from a laser light."
See the complete Mayo news release:
http://www.mayoclinic.org/news2005-rst/2800.html
I would like to have anyone point out to me the harm an "astronomical"
GLP has done to the eyes of a person who was NOT involved in an
experiment. I know several people have been arrested for shining GLPs
at planes when they are landing but I am sure that no permanent damage
was caused to any crew member or passenger.
I use GLPs for educational purposes and as a finder (to supplement my
standard finder) on my dobsonian.
Under near perfect sky conditions try pointing out the Andromeda
galaxy with your finger to a school kid and the kid will learn
nothing. But use a GLP, especially one mounted on a stable telescope
pointed at the galaxy, and there is a good chance that the student
will see this smudge of light without benefit of the telescope.
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Date: 06 Aug 2007 13:54:58
From: beowulf@nowhere.net
Subject: Re: pocket lasers for star pointing?
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On Aug 6, 8:47 am, "DH" <dark_hel...@chinsawcraver.org > wrote:
> red lasers didn't do damage. Green did.
...
good to know. I will treat the green laser like a loaded weapon and
never ever point it anybody.
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Date: 06 Aug 2007 12:25:58
From: beowulf@nowhere.net
Subject: Re: pocket lasers for star pointing?
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On Aug 5, 10:43 pm, Chris L Peterson <c...@alumni.caltech.edu > wrote:
> Fortunately, this system is very safe- especially the cheapest ones. ..
I was thinking it must be safe-- I read some article yesterday on the
net about these 5mw astronomy lasers and apparently a medical study
was done, with subjects staring for 15 minutes into the lasers. No
noticiable eye damage was done by the lasers (subjective, and also
biopsied eyes, etc). The subjects were having their eyes removed for
medical reasons anyhow (tumors I suspect), so there was no risk to
them regardless of what the lasers might do. I still plan to be
pretty careful and not point the laser at anybody (I will treat it
like a firearm, which I would never point at anybody, always treat it
as loaded/dangerous).
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Date: 06 Aug 2007 09:47:58
From: DH
Subject: Re: pocket lasers for star pointing?
|
red lasers didn't do damage. Green did.
http://www.revoptom.com/index.asp?page=2_1451.htm
.
.
.
"Some 24 hours after exposure, the researchers observed retinopathy,
characterized by a yellowish discoloration, at the level of the retinal
pigment epithelium (RPE) in the subfoveal section and at the location above
the fovea that were exposed to the green beam for 15 minutes. At the six-day
follow-up, they observed delicate granular irregularity at the level of the
RPE"
.
.
.
"The researchers conclude that this study should be a warning that exposure
of the retina to light from a commercially available green laser pointer
carries a real risk, and this risk appears to surpass that of the
commercially available red laser pointers"
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Date: 06 Aug 2007 08:34:38
From: Chris L Peterson
Subject: Re: pocket lasers for star pointing?
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On Mon, 6 Aug 2007 09:47:58 -0400, "DH" <dark_helmet@chinsawcraver.org >
wrote:
>red lasers didn't do damage. Green did.
>
>http://www.revoptom.com/index.asp?page=2_1451.htm
This type of retinal discoloration has also been observed after
sustained exposure to red lasers. It has not been observed to be
permanent, however. This study suggests that extended exposure to a
focused 5mW green laser may produce temporary retinal damage.
The important point, however, is that damage requires sustained
exposures, far longer than are possible by accident. We are surrounded
by things that are safe at the level of brief accidental exposure, but
are dangerous or even deadly given a long, deliberate exposure.
_________________________________________________
Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com
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Date: 06 Aug 2007 07:39:41
From: Chris L Peterson
Subject: Re: pocket lasers for star pointing?
|
On Mon, 06 Aug 2007 12:25:58 -0000, "beowulf@nowhere.net"
<r.oelerich@gmail.com > wrote:
>I was thinking it must be safe-- I read some article yesterday on the
>net about these 5mw astronomy lasers and apparently a medical study
>was done, with subjects staring for 15 minutes into the lasers. No
>noticiable eye damage was done by the lasers (subjective, and also
>biopsied eyes, etc). The subjects were having their eyes removed for
>medical reasons anyhow (tumors I suspect), so there was no risk to
>them regardless of what the lasers might do. I still plan to be
>pretty careful and not point the laser at anybody (I will treat it
>like a firearm, which I would never point at anybody, always treat it
>as loaded/dangerous).
That's a reasonable way to handle it.
There are two issues of safety. The first is the beam itself in a
properly functioning system. It is widely considered that a 5mW visible
laser is safe, in that it cannot reasonably produce any eye damage
(although in some situations it might dazzle, causing a dangerous
situation). The second is danger from a malfunctioning system. A green
laser pointer does contain an internal IR laser that is plenty powerful
enough to cause retinal damage (even skin damage). Fortunately, the way
that the laser modules are designed makes it extremely unlikely that
this IR can escape with sufficient energy and collimation to be
hazardous.
_________________________________________________
Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com
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Date: 05 Aug 2007 22:15:27
From: beowulf@nowhere.net
Subject: Re: pocket lasers for star pointing?
|
On Aug 5, 4:54 pm, Davoud <s...@sky.net > wrote:
> I still think you need to get the laser pointer out of your head. I
> know it seems like a really neat thing to own. That's why I bought one
> a couple of years ago -- the one I have never used. Not once. It's a
> limited use item that weighs you down. Focus on learning the
> constellations and the bright stars and when someone tells you that an
> object is a fist southwest of Altair you will find it visually (if that
> is possible) or with your 'scope without the need for a laser.
Haha, oh man one minute too late-- I just got done ordering online a
<5mw green laser.
http://store.nexternal.com/shared/StoreFront/default.asp?CS=jmm6360&BusType=BtoC&Count1=836589992&Count2=753730416&ProductID=54&Target=products.asp
It might make a nice paper weight, who knows. I like the matte black
look of it; what can I say I am also a techno-geek linux and open
source computer user, love my toys! In the least it might make a sexy
tech toy to entice a lady out on a starry night for gazing.
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Date: 06 Aug 2007 01:21:17
From: Bill Cheeseman
Subject: Re: pocket lasers for star pointing?
|
"beowulf@nowhere.net" <r.oelerich@gmail.com > wrote in message
news:1186352127.375405.244310@m37g2000prh.googlegroups.com...
> On Aug 5, 4:54 pm, Davoud <s...@sky.net> wrote:
>> I still think you need to get the laser pointer out of your head. I
>> know it seems like a really neat thing to own. That's why I bought one
>> a couple of years ago -- the one I have never used. Not once. It's a
>> limited use item that weighs you down. Focus on learning the
>> constellations and the bright stars and when someone tells you that an
>> object is a fist southwest of Altair you will find it visually (if that
>> is possible) or with your 'scope without the need for a laser.
>
> Haha, oh man one minute too late-- I just got done ordering online a
> <5mw green laser.
> http://store.nexternal.com/shared/StoreFront/default.asp?CS=jmm6360&BusType=BtoC&Count1=836589992&Count2=753730416&ProductID=54&Target=products.asp
> It might make a nice paper weight, who knows. I like the matte black
> look of it; what can I say I am also a techno-geek linux and open
> source computer user, love my toys! In the least it might make a sexy
> tech toy to entice a lady out on a starry night for gazing.
Be very careful with it once it arrives. Green lasers, because of their
design, emit infrared as well as green light. If the pointer is properly
made, the infrared will be filtered out and only green light emitted, but if
not you'll have infrared to contend with. Stray reflections are bad enough
from green light, but if IR is also present, the eyes don't compensate for
it and eye damage can easily result. Best advice is to find out if the
pointer you bought also has an infrared filter within. If not, I would
suggest returning it and obtaining a pointer that is sure to be IR filtered.
This IR issue has become more commonplace since many cheaper pointers are
coming out of China, even nearly identical "clones" to American and other
pointers except no IR filter and other shortcuts to save costs.
Bill
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Date: 06 Aug 2007 02:42:07
From: Sam Wormley
Subject: Re: pocket lasers for star pointing?
|
Bill Cheeseman wrote:
> "beowulf@nowhere.net" <r.oelerich@gmail.com> wrote in message
> news:1186352127.375405.244310@m37g2000prh.googlegroups.com...
>> On Aug 5, 4:54 pm, Davoud <s...@sky.net> wrote:
>>> I still think you need to get the laser pointer out of your head. I
>>> know it seems like a really neat thing to own. That's why I bought one
>>> a couple of years ago -- the one I have never used. Not once. It's a
>>> limited use item that weighs you down. Focus on learning the
>>> constellations and the bright stars and when someone tells you that an
>>> object is a fist southwest of Altair you will find it visually (if that
>>> is possible) or with your 'scope without the need for a laser.
>> Haha, oh man one minute too late-- I just got done ordering online a
>> <5mw green laser.
>> http://store.nexternal.com/shared/StoreFront/default.asp?CS=jmm6360&BusType=BtoC&Count1=836589992&Count2=753730416&ProductID=54&Target=products.asp
>> It might make a nice paper weight, who knows. I like the matte black
>> look of it; what can I say I am also a techno-geek linux and open
>> source computer user, love my toys! In the least it might make a sexy
>> tech toy to entice a lady out on a starry night for gazing.
>
> Be very careful with it once it arrives. Green lasers, because of their
> design, emit infrared as well as green light. If the pointer is properly
> made, the infrared will be filtered out and only green light emitted, but if
> not you'll have infrared to contend with. Stray reflections are bad enough
> from green light, but if IR is also present, the eyes don't compensate for
> it and eye damage can easily result. Best advice is to find out if the
> pointer you bought also has an infrared filter within. If not, I would
> suggest returning it and obtaining a pointer that is sure to be IR filtered.
> This IR issue has become more commonplace since many cheaper pointers are
> coming out of China, even nearly identical "clones" to American and other
> pointers except no IR filter and other shortcuts to save costs.
>
> Bill
>
>
My green laser converts UV to green.
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Date: 05 Aug 2007 21:43:46
From: Chris L Peterson
Subject: Re: pocket lasers for star pointing?
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On Mon, 06 Aug 2007 02:42:07 GMT, Sam Wormley <swormley1@mchsi.com >
wrote:
> My green laser converts UV to green.
What the heck kind of laser is that? It's tough enough to generate UV
with a semiconductor to begin with. And I don't know any non-linear
materials that halve the frequency. Maybe you have some sort of gas or
dye laser in the lab?
All green laser pointers I know of use an 808nm laser to pump a doped Nd
crystal at 1064nm, and then send that through a KTP frequency doubler to
produce the final 532nm output.
Fortunately, this system is very safe- especially the cheapest ones. The
frequency doubler is part of the cavity, and if it fails in any way the
IR source stops lasing as well. Between the high efficiency of the
frequency doubler, and the fact that the collimator is the wrong power
for the IR beam, it is almost impossible to get a dangerous amount of IR
out the end of a GLP, even if there is no IR blocking filter. Warnings
abound about this supposed danger, but I've never heard of an actual
case in reality.
_________________________________________________
Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com
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Date: 06 Aug 2007 04:01:44
From: Sam Wormley
Subject: Re: pocket lasers for star pointing?
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Chris L Peterson wrote:
> On Mon, 06 Aug 2007 02:42:07 GMT, Sam Wormley <swormley1@mchsi.com>
> wrote:
>
>> My green laser converts UV to green.
>
> What the heck kind of laser is that? It's tough enough to generate UV
> with a semiconductor to begin with. And I don't know any non-linear
> materials that halve the frequency. Maybe you have some sort of gas or
> dye laser in the lab?
>
> All green laser pointers I know of use an 808nm laser to pump a doped Nd
> crystal at 1064nm, and then send that through a KTP frequency doubler to
> produce the final 532nm output.
>
> Fortunately, this system is very safe- especially the cheapest ones. The
> frequency doubler is part of the cavity, and if it fails in any way the
> IR source stops lasing as well. Between the high efficiency of the
> frequency doubler, and the fact that the collimator is the wrong power
> for the IR beam, it is almost impossible to get a dangerous amount of IR
> out the end of a GLP, even if there is no IR blocking filter. Warnings
> abound about this supposed danger, but I've never heard of an actual
> case in reality.
>
> _________________________________________________
>
> Chris L Peterson
> Cloudbait Observatory
> http://www.cloudbait.com
That makes sense for my green laser purchased in 2002. It is 532 nm,
but I could have sworn the documentation (which I cannot find, of course)
indicated a down conversion from UV. Until I can find otherwise, I will
assume you are correct and mime converts 808 nm to 532 nm.
--Sam
Label:
Max output < 5 mW
Wavelength 532 nm
CLASS IIIa LASER Product
Manufactured by Leadlight Technology, Inc., Taiwan
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Date: 05 Aug 2007 21:45:48
From: beowulf@nowhere.net
Subject: Re: pocket lasers for star pointing?
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On Aug 5, 12:38 pm, Chris L Peterson <c...@alumni.caltech.edu > wrote:
> Green laser pointers work well for pointing out stars. I don't see how
> one would be helpful for learning the sky, however, unless you're
> working with other people....
That is what I was thinking of doing, use a laser when out with
someone else so we could communicate about what star we are both
trying to look for, etc., otherwise it is hard to say "That white dot
up over there". :) Definitely star charts too.
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Date: 06 Aug 2007 14:42:17
From: Jim Dubya
Subject: Re: pocket lasers for star pointing?
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The high power laser are more fun because you can point out stars really
well, and when it is a cloudy night, you can have a lot of fun popping
balloons.
"beowulf@nowhere.net" <r.oelerich@gmail.com > wrote in message
news:1186350348.392178.267110@x35g2000prf.googlegroups.com...
> On Aug 5, 12:38 pm, Chris L Peterson <c...@alumni.caltech.edu> wrote:
>> Green laser pointers work well for pointing out stars. I don't see how
>> one would be helpful for learning the sky, however, unless you're
>> working with other people....
>
> That is what I was thinking of doing, use a laser when out with
> someone else so we could communicate about what star we are both
> trying to look for, etc., otherwise it is hard to say "That white dot
> up over there". :) Definitely star charts too.
>
>
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Date: 05 Aug 2007 21:54:34
From: Davoud
Subject: Re: pocket lasers for star pointing?
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Chris L Peterson:
> > Green laser pointers work well for pointing out stars. I don't see how
> > one would be helpful for learning the sky, however, unless you're
> > working with other people....
beowulf@nowhere.net:
> That is what I was thinking of doing, use a laser when out with
> someone else so we could communicate about what star we are both
> trying to look for, etc., otherwise it is hard to say "That white dot
> up over there". :) Definitely star charts too.
I still think you need to get the laser pointer out of your head. I
know it seems like a really neat thing to own. That's why I bought one
a couple of years ago -- the one I have never used. Not once. It's a
limited use item that weighs you down. Focus on learning the
constellations and the bright stars and when someone tells you that an
object is a fist southwest of Altair you will find it visually (if that
is possible) or with your 'scope without the need for a laser.
Davoud
--
usenet *at* davidillig dawt com
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Date: 05 Aug 2007 20:57:27
From: Davoud
Subject: Re: pocket lasers for star pointing?
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beowulf@nowhere.net:
> Before I buy a telescope, I want to get out and learn basic
> constellations, etc, naked eye and binoculars. But I see in magazines
> there little pocket lasers for pointing up in the sky. Are they really
> worth it, useful? They are priced by wattage, what sort of wattage is
> typically needed? I see 35mw models for $170, 125mw models for $550.
Forget the laser. Laser pointers are used by persons who know the night
sky well to point out the positions of objects to the uninitiated or to
other amateurs who don't know the sky so well. They are of no use
whatsoever in learning the sky.
Get a planisphere and a star atlas such as those sold by Sky &
Telescope.
Start with your naked eye and the planisphere. Note that the
planisphere instructions don't emphasize enough that it is a /sphere/
imposed on a plane surface. Stick to the brightest stars at first. As
you face southward and hold the plani /sphere/ in front of you with the
appropriate date set on the plani sphere you should, after a bit, be
able to relate one or two bright stars in the sky with what you see on
the planisphere. That will be an epiphany because it will suddenly
explain the planisphere and show you the scale of things. Then note
that Polaris, shown toward the top of the planisphere, is in fact on
the other side of the sphere -- somewhere directly behind your head if
you are looking south. When I got my first planisphere I held it high,
well above eye level, at first in order to achieve better perspective.
Go from there. I'll avoid clichés like "The sky's the limit." If you
learn the basics with your naked eye and hunger for more you can switch
to binoculars to see and memorize more asterisms (chance star patterns,
not necessarily corresponding to constellation patterns) that will help
you find your way around the sky.
Davoud
--
usenet *at* davidillig dawt com
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Date: 05 Aug 2007 11:38:52
From: Chris L Peterson
Subject: Re: pocket lasers for star pointing?
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On Sun, 05 Aug 2007 16:41:13 -0000, "beowulf@nowhere.net"
<r.oelerich@gmail.com > wrote:
>Before I buy a telescope, I want to get out and learn basic
>constellations, etc, naked eye and binoculars. But I see in magazines
>there little pocket lasers for pointing up in the sky. Are they really
>worth it, useful? They are priced by wattage, what sort of wattage is
>typically needed? I see 35mw models for $170, 125mw models for $550.
Green laser pointers work well for pointing out stars. I don't see how
one would be helpful for learning the sky, however, unless you're
working with other people. What a laser does is lets a person point out
objects to other people. For learning the sky, a good old fashioned
planisphere is great (and only about $10).
Laser's are sold with a classification system that dictates power.
Although it is legal to buy, and in most cases use, high powered lasers
(in the U.S., at least), virtually all laser pointers are sold as class
IIIa devices, with a maximum output of 5mW (which is quite safe). Nearly
all of the high power green lasers are modified class IIIa devices, and
most still have class IIIa stickers on them (which is illegal). Should
you injure somebody with a laser pointer, I'm sure your liability is
considerably greater if that laser isn't a class IIIa.
In nearly all cases, 5mW is plenty of power for a pointer used for
pointing out stars. If you decide to get one, don't go for more power.
Good 5mW pointers can be had for under $50.
_________________________________________________
Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com
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