Pot modding to lower power?

[thecelloronin]

Hello all,

I know this is a touchy subject around here that gets asked by newbies (like me) all too often. Before going any further, I'll disclaimer that I made fairly liberal use of the search function, and found this important tidbit to sum up the general consensus around pot modding:

Pot modding is never a good idea any more. There was a time years ago when green lasers were new on the market and most manufacturers were just churning them out without binning them. Then you could often pot mod a laser safety and get a few mW more out when you happened upon a unit with better efficiency than normal. Those days are long gone. Manufacturers bin their units now - their 1mW, 5mW, 15mW, etc models are all exactly the same inside, they just make one model and sort them by how much power they can squeeze out of it. That is why you can't safely pot mod any more, cheap green pointers are already turned up to the maximum they can take before they leave the retailer. This is part of why they are so much more inexpensive now than they were years ago. Manufacturers get tons of low output ones via the binning process.

That said, I understand that pot-modding kills lasers primarily because the goal is to increase output, despite modern manufacturers already shipping GLPs set to max. But, what about pot modding specifically to achieve variable attenuation?

My use-case is astronomy. Depending on the ambient light pollution, I might want the full ~5mW for visibility when pointing the scope, but at a dark site a 5mW beam is overwhelming, washing out your target and ruining your night adapted vision even with just a flash. Thus, being able to lower the power would be mightily useful.

Does this nevertheless run the risk of burning out your GLP?

If this has been answered before, please feel free to crucify me (but please do provide a link–I clearly missed it during search). In any case, thanks for your time.

 

[hakzaw1]

why?
just buy another $3 GLP
very few are the same mW
almost all RGB pointers will be much more than 5 mW each.
I have one TRUE 532 5mW used to calibrate and they sell for $140.

 

[thecelloronin]

$3 GLPs are ill-suited to astronomy for a number of reasons, most primarily due to unreliability in the cold outdoors. Indeed, I spent quite a bit extra on my Z-Bolt laser for low temperatures down to 14°. And, given our goal is to have well-dilated eyes, the typical lack of IR filtration in cheap lasers is generally seen as something to be avoided for safety reasons. Moreover, switching out between pointers mounted on the scope to fit the locale's light pollution level is a pain since you have to realign the laser with the primary objective.

Howie Glatter made a physical component for his laser collimators that allows for manual (non electrical) attenuation of brightness, but short of shelling out nearly $500 for one of those systems, I'd prefer to DIY a solution if possible.

 

[hakzaw1]

please combine posts. The forum frowns upon doubles etc.

 

[thecelloronin]

Thanks for the heads up, I've edited my last message accordingly.

My Z-Bolt retails for $98, so it's not exactly cheap. I trust them to be fairly exact when they specify between 4 and 5mW

 

[ArcticDude]

here you go: You can adjust output via TTL signal
Green is direct diode so cold weather doesn't affect the laser

Survelase - Global Laser

Wavelengths of green (520nm) and red (635, 650nm) are available with output powers up to 5mW. The green model emits light that appears more than 2X brighter

www.global-lasertech.co.uk

 

[hakzaw1]

yr welcome
help me understand (I have never used any laser for constellations or aiming at a stars or planets.)
I assumed you use the green pointer only long enough to point towards or 'hit' your object.
that should not cause much change in our eyes --if brief and NOT aimed anywhere else. Green diode lasers are less bright --and getting cheaper.
I would worry more about over-heating damage. Pen Pointers have almost no heat sink
==btw Zbolt makes great lasers.
you may b want to consider making an 'intro' of yourself and add a location in the intro & your profile-- 'laser folks' are all great people--I have been blessed meeting MYB 100 forum members by attending and hosting Meet ( LEMs) we cannot invite you w/o more info-WELCOME to LPF ENJOY!! hak

 

[thecelloronin]

ArcticDude – Very cool, this gives me something to look into. That said, anecdotal evidence shows that lesser GLPs can definitely suffer for our purposes in the cold. Any idea whether that laser you posted has IR filtration? A quick glance doesn't show, but I probably need to look around a bit more closely.

hazkaw1 – Right on, I'll get to work on that, thanks for the welcome. It's true the laser won't be on for too terribly long, but even 30 seconds to a minute can be enough to "ruin" dark adaptation. In general, we try to push our pupils as close to 7mm (or some people go even wider), which takes about 30 minutes in PROPERLY DARK skies. Your eyes won't ever get there in suburban light pollution, so for purposes of spotting in my front yard, you're absolutely right that the brief flash of laser won't be too bad.

Understand, though, when we're searching for faint galaxies, globular clusters, nebulae, and other things that are barely visible, we're not even using the cones in our eyes, but the rods through a technique known as averted vision. (I'd link you to some reading, but I don't have the 10 posts necessary yet. Basically, you can detect greater differences in faint light with the rods of your eyes, which are I think more towards the periphery of your vision. Rather than looking directly at a deep space object, you look a little off to the side and you'll see more detail. It's crazy the first time you see it.) So, dark adaptation for astronomy is quite sensitive! Many actually prefer blue laser pointers which aren't as bright, but in many cases still too bright.

 

[ArcticDude]

ArcticDude – Very cool, this gives me something to look into. That said, anecdotal evidence shows that lesser GLPs can definitely suffer for our purposes in the cold. Any idea whether that laser you posted has IR filtration? A quick glance doesn't show, but I probably need to look around a bit more closely.

hazkaw1 – Right on, I'll get to work on that, thanks for the welcome. It's true the laser won't be on for too terribly long, but even 30 seconds to a minute can be enough to "ruin" dark adaptation. In general, we try to push our pupils as close to 7mm (or some people go even wider), which takes about 30 minutes in PROPERLY DARK skies. Your eyes won't ever get there in suburban light pollution, so for purposes of spotting in my front yard, you're absolutely right that the brief flash of laser won't be too bad.

Understand, though, when we're searching for faint galaxies, globular clusters, nebulae, and other things that are barely visible, we're not even using the cones in our eyes, but the rods through a technique known as averted vision. (I'd link you to some reading, but I don't have the 10 posts necessary yet. Basically, you can detect greater differences in faint light with the rods of your eyes, which are I think more towards the periphery of your vision. Rather than looking directly at a deep space object, you look a little off to the side and you'll see more detail. It's crazy the first time you see it.) So, dark adaptation for astronomy is quite sensitive! Many actually prefer blue laser pointers which aren't as bright, but in many cases still too bright.

520nm Direct diode doesn't emit IR

 

[hakzaw1]

ArcticDude – Very cool, this gives me something to look into. That said, anecdotal evidence shows that lesser GLPs can definitely suffer for our purposes in the cold. Any idea whether that laser you posted has IR filtration? A quick glance doesn't show, but I probably need to look around a bit more closely.

hazkaw1 – Right on, I'll get to work on that, thanks for the welcome. It's true the laser won't be on for too terribly long, but even 30 seconds to a minute can be enough to "ruin" dark adaptation. In general, we try to push our pupils as close to 7mm (or some people go even wider), which takes about 30 minutes in PROPERLY DARK skies. Your eyes won't ever get there in suburban light pollution, so for purposes of spotting in my front yard, you're absolutely right that the brief flash of laser won't be too bad.

Understand, though, when we're searching for faint galaxies, globular clusters, nebulae, and other things that are barely visible, we're not even using the cones in our eyes, but the rods through a technique known as averted vision. (I'd link you to some reading, but I don't have the 10 posts necessary yet. Basically, you can detect greater differences in faint light with the rods of your eyes, which are I think more towards the periphery of your vision. Rather than looking directly at a deep space object, you look a little off to the side and you'll see more detail. It's crazy the first time you see it.) So, dark adaptation for astronomy is quite sensitive! Many actually prefer blue laser pointers which aren't as bright, but in many cases still too bright.

dont know how well this would work--i hate the blue headlights- screws up my night vision- to help some I often close one eye or block with hand--that way at least one eye should still be fairly adapted.
nice thread!!
hak

 

[gazer101]

The problem is that most lasers have a minimum lasing threshold... some cannot output less than 50mW lest they turn into LEDs.

Sometimes you run into super weak lasers on Aliexpress. I coincidentally bought a 1mW red (looks way dimmer than an actual 5mW) but I'm sure there are greens there too.

Then its a matter of overdriving said <1mW laser to 5mW using an LPM to ensure it is at the target power

 

[thecelloronin]

Hey folks,

I posted this topic over on Cloudy Nights, the major US astronomy geek forum. Sadly, the mods had to remove it because GLPs are a touchy subject, and any mods which could in any way pose a danger is something they remove as a matter of policy. No hard feelings, I get it.

That said, I did get an interesting suggestion to built a rotatable polarizing filter in front of the laser, before it the topic got removed. Anyone have any idea of how to do this, or heard of it being done?

There's also an interesting invention by the late Howie Glatter, who made bullet-proof laser collimators. He built a "VLB" (variable laser brightness) unit which would replace the power cap of his lasers. Again, I'm too new to post links, but you can google "Glatter VLB collimator" and find the product on collimator dot com. I'm in no way shilling for the company, just pointing it out as an interesting, if expensive solution.

I'm still looking into TTL circuits and that laser that ArcticDude posted, though all this warning of danger has me mayyyyybe just a little bit second guessing my amateur electronic skills.

And hakzaw1, closing one eye is actually a pretty smart idea... brilliant even.

 

[gazer101]

Why bother getting expensive optics to tame a powerful laser when you can just buy a weak laser to begin with?

 

[Mattronium]

520nm diode lasers would not have any issues with lower temperature instabilities.
Does the laser power need to be adjustable in the field or just once? I would suspect that pot-modding it should be OK, but without knowing the circuit it is hard to know for sure.

Putting a polarizing filter in is a decent option. Just get a 520nm diode pointer and adding a polarizing filter to it. Then the polarizing filter can be rotated to select the transmission power. This option is not perfect and might have issues with light scatter off the filter, but it is an option. I have done this to a cheap ebay pen host, just took the cap off, cut a piece from some plastic sunglasses, and stuffed it into the cap.

 

[ArcticDude]

I'm still looking into TTL circuits and that laser that ArcticDude posted, though all this warning of danger has me mayyyyybe just a little bit second guessing my amateur electronic skills.

And hakzaw1, closing one eye is actually a pretty smart idea... brilliant even.

Well PWM generators are pretty cheap..

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EDIT
LambdaWave 5mW TTL modules are little cheaper 110 USD

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