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Green Laser Pointers, and Dark Adaptation

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#1 mayidunk

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Posted 23 August 2013 - 03:52 AM

If viewed through the eyepiece, can a green laser pointer's beam cutting across the field of view, and being magnified, actually affect your eye's dark adaptation? (Just to be clear, I'm not talking about the pointer shining directly into the OTA, but about its upwardly directed beam crossing through your telescope's field of view.)

:question:

#2 nicknacknock

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Posted 23 August 2013 - 05:31 AM

Yes, it does.

#3 wags1

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Posted 23 August 2013 - 07:27 AM

Very minimally. That said, other than initial alignment of the GLP (if being used as a finder), there should be no reason to have the GLP on when you are looking thru the EP.

#4 hottr6

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Posted 23 August 2013 - 07:29 AM

This is how I use my GLP as a finder; I can see the end of the beam in the center of the FOV of my eyepiece. The beam is not as bright as you may think, and while there may be some degradation of dark adaption, I honestly do not notice it.

#5 Jarad

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Posted 23 August 2013 - 07:32 AM

The answer will depend a lot on how dark adapted you are to start with. If you are in an urban area, you probably won't get fully dark adapted anyway, and the GLP won't make much difference. If you are at a truly dark site and have let your eyes adapt for an hour, and are hunting dim fuzzies, it could set you back a few minutes while your eyes re-adapt.

Jarad

#6 wags1

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Posted 23 August 2013 - 08:30 AM

This is how I use my GLP as a finder; I can see the end of the beam in the center of the FOV of my eyepiece. The beam is not as bright as you may think, and while there may be some degradation of dark adaption, I honestly do not notice it.

I'm wondering how you are using your GLP as a finder. To explain what I mean, this is how I use mine. I pick my first alignment star. Once the scope slews to the spot where it thinks the first alignment star is I press and hold the remote instant on/off pressure switch for my GLP. While holding the switch "on" I use the arrow keys of my handbox and slew the scope so that the laser beam touches the alignment star. I then let go of the switch and look in the EP. Normally at that point the star is close to center or at least somewhere I can see it in the EP (the better you do at the initial alignment/setup of your GLP the closer it will be to dead center at this point). While looking in the EP (GLP still off) I make the final adjustments to get the alignment star dead center. I repeat that process for the second alignment star. At no time is my GLP on when I am looking into the EP.
I'm not saying this is the only process to be used, but I don't understand what is gained by looking in the EP with the GLP on.

#7 Jarad

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Posted 23 August 2013 - 08:33 AM

I'm not saying this is the only process to be used, but I don't understand what is gained by looking in the EP with the GLP on.



Normally would just do this to confirm that the GLP is aligned with where the scope it pointing (i.e. when you are first aligning the GLP). After that, you might do it again just to check the alignment. But you are right, you normally wouldn't need to observe while it is on.

Jarad

#8 wags1

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Posted 23 August 2013 - 09:23 AM

IMHO, the one "must have" GLP accessory, in addition to the mount obviously, is a remote instant on/off switch. Basically a pressure switch on the end of a short wire. It provides two important functions. One, it allows you to turn your GLP on/off without causing any vibrations or movement of your scope. And two, it allows you to use your GLP in very short bursts which is typically all you ever need.

#9 Qwickdraw

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Posted 23 August 2013 - 10:59 AM

The laser sold at Orion has a ring attachment with 3 setscrews and 1 forth thumb screw to turn onto the momentary on/off pushbutton. It seems to work consistently.

#10 hottr6

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Posted 23 August 2013 - 11:44 AM

I'm not saying this is the only process to be used, but I don't understand what is gained by looking in the EP with the GLP on.



Normally would just do this to confirm that the GLP is aligned with where the scope it pointing (i.e. when you are first aligning the GLP). After that, you might do it again just to check the alignment. But you are right, you normally wouldn't need to observe while it is on.

Affirmative. I was answering the OP's question of does the GLP beam viewed through the eyepiece affect dark-adaption. Once I have verified parallelism of OTA and GLP, there is never any need to view the beam in the eyepiece.

#11 mayidunk

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Posted 23 August 2013 - 08:53 PM

I'm not saying this is the only process to be used, but I don't understand what is gained by looking in the EP with the GLP on.



Normally would just do this to confirm that the GLP is aligned with where the scope it pointing (i.e. when you are first aligning the GLP). After that, you might do it again just to check the alignment. But you are right, you normally wouldn't need to observe while it is on.

Affirmative. I was answering the OP's question of does the GLP beam viewed through the eyepiece affect dark-adaption. Once I have verified parallelism of OTA and GLP, there is never any need to view the beam in the eyepiece.

Actually, I was thinking more about how it might affect another person. If I was thoroughly dark adapted trying to tease detail out of a dim galaxy when suddenly a GLP beam appear in my FOV, I imagine that would disappoint me just a wee bit. I would hate to think that I might be doing that to someone else.

#12 star drop

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Posted 23 August 2013 - 09:38 PM

It definitely affects one's dark adaptation as viewed in a green zone with less than an hour of dark adaptation. A person using a laser within a fifty foot radius can make M51 turn green in your eyepiece.

#13 Bill Weir

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Posted 23 August 2013 - 11:33 PM

Luckily the people I observe with don't use one of these devices as a finder. On the rare occasion when I've been somewhere where a laser did happen to go across my FOV bad words leapt out of my mouth. Usually I observe alone and happily the star parties I attend have banned GLPs.

I agree with Jarad I think the amount of light pollution you observe from affects how much you are affected. The more LP you are in the less other light will bother you. Light is light. If you are in a fairly dark place any light will affect you. Actually when I'm out with others it's those stupid red headlamps that so many observers (especially the imagers) are starting to wear that bother e more than lasers. Turn them OFF when we are talking to each other. Your ears will still work even if yu an't see my face and my eyes will still work when we are finished.

Bill

#14 Jon Isaacs

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Posted 24 August 2013 - 11:12 AM

I wonder if the bright green dazzle of the beam used naked eye as a pointer affects dark adaptation?

Jon

#15 mayidunk

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Posted 24 August 2013 - 02:40 PM

I wonder if the bright green dazzle of the beam used naked eye as a pointer affects dark adaptation?

Jon

So, given this, why do so many seem to gravitate towards using GLPs? Isn't this kind of like people shining flashlights into each others' faces?

#16 SteveG

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Posted 24 August 2013 - 04:42 PM

I wonder if the bright green dazzle of the beam used naked eye as a pointer affects dark adaptation?

Jon

So, given this, why do so many seem to gravitate towards using GLPs? Isn't this kind of like people shining flashlights into each others' faces?


There is no "given" there, he was asking the question. My answer would be no. I've used a GLP at many dark sky outings, and the light has not been bright enought to reduce my night vision. Granted, I have older eyes, so YMMV.

If using a laser was equal to shining a flashlight is someone's face, then no one would be using them.

#17 Jon Isaacs

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Posted 24 August 2013 - 05:04 PM

I've used a GLP at many dark sky outings, and the light has not been bright enought to reduce my night vision.



Exactly how can one be sure that ones dark adaptation has not been affected?

Jon

#18 Scanning4Comets

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Posted 25 August 2013 - 10:36 PM

Actually when I'm out with others it's those stupid red headlamps that so many observers (especially the imagers) are starting to wear that bother e more than lasers. Turn them OFF when we are talking to each other. Your ears will still work even if you can't see my face and my eyes will still work when we are finished.

Bill


Oh god, I hate when this happens. I always have to tell them to "please turn off your headlamps" :ranting: :lol:

#19 Shneor

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Posted 26 August 2013 - 01:41 AM

I've used a GLP at many dark sky outings, and the light has not been bright enought to reduce my night vision.



Exactly how can one be sure that ones dark adaptation has not been affected?

Jon

Just check that limiting magnitude star and determine if it is still visible. I sometimes - not often - use a violet laset pointer (405nm) to point out constellations or object locations. It does not appear to affect my night vision (in any case, it's only visible to my left eye; my right eye can't see it, and that's my dominant eye).

Clears,

#20 izar187

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Posted 26 August 2013 - 06:10 AM

I wonder if the bright green dazzle of the beam used naked eye as a pointer affects dark adaptation?

Jon

So, given this, why do so many seem to gravitate towards using GLPs? Isn't this kind of like people shining flashlights into each others' faces?


Ego, grand standing, being the self appointed wizard of others' night sly....

I've had many a green beam cross my ep field at public outreach when trying to show guests something through a scope, that they might never see without a scope. But the intrusive beam often quickly becomes the show. "Wow, what was that?" Commonly followed by "Where can I get one of those?" With luck and patience they might actually see a bit of the structure or shape of the intended target, or it's companions. But frequently it's off to find the pretty green light.

#21 Brent Campbell

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Posted 26 August 2013 - 06:21 AM

I wonder if the bright green dazzle of the beam used naked eye as a pointer affects dark adaptation?

Jon

So, given this, why do so many seem to gravitate towards using GLPs? Isn't this kind of like people shining flashlights into each others' faces?



Simple, bad back, don't want to get into contorted positions to view through the finder. If used responsibly then theres no issue.

#22 izar187

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Posted 26 August 2013 - 06:58 AM

I wonder if the bright green dazzle of the beam used naked eye as a pointer affects dark adaptation?

Jon

So, given this, why do so many seem to gravitate towards using GLPs? Isn't this kind of like people shining flashlights into each others' faces?



Simple, bad back, don't want to get into contorted positions to view through the finder. If used responsibly then theres no issue.



Absolutely!
The folks who are rightly using them for their finders, their minimal intensity beams are not the ones in other peoples eyepiece fields.

#23 Jarad

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Posted 26 August 2013 - 09:52 AM

Ego, grand standing, being the self appointed wizard of others' night sly....

I've had many a green beam cross my ep field at public outreach when trying to show guests something through a scope, that they might never see without a scope.



That's a bit harsh. Using a GLP at a public outreach to point out constellations, planets, or the object they just saw through the scope is actually a good teaching tool. I don't think you should automatically assign such derogatory motivations - getting people interested in looking up at the sky is the point of those events, after all.

Jarad

#24 Jon Isaacs

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Posted 26 August 2013 - 10:15 AM

That's a bit harsh. Using a GLP at a public outreach to point out constellations, planets, or the object they just saw through the scope is actually a good teaching tool.


I think with a large crowd, it is difficult without a pointer but with a few people, I still believe the pointing the fingers with the detailed discussion is a better teaching tool. (9 o'clock from...) With the laser, you just show them, where it is, it's fast and easy.

With the old fashioned techniques, it's slower but there is more learning about how to navigate the night sky. People need to think, they need to observe closely what they are seeing. When all is said and done, I believe someone is more likely to remember what they have seen, how to find it again because they have been involved with their eyes and mind in the discovery process.

It is also more engaging, rather than me telling people with a narrative, it's back and forth between not only myself but everyone, until they do see it.

Jon

#25 Jarad

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Posted 26 August 2013 - 10:31 AM

There are a wide variety of ways to teach.

I was at the Indiana Family Star Gaze a few years ago, and they had a great program for the kids. During the afternoon, they did a slide show going over a number of constellations. Then in the evening they did a challenge game for the kids, where they won prizes for being to use a GLP to point out the constellations themselves. This got the kids very excited and involved, and pointing it out yourself requires you to recognize the constellation first.

Obviously you can teach the constellations without a GLP. And different teaching styles will work better with different students. But I still think the GLP is a useful teaching tool. It doesn't replace thinking, visualizing, etc., but it can be a good supplement to them. Yes, they are fun. There's nothing wrong with making learning fun.

With kids, it can also be used to teach a bit of responsibility. Before they got to use the GLP, we went over the rules. In addition to basic safety, we discussed courtesy - don't swing it all over the sky, aim where you intend to point before pressing the on button, release the on button before moving to the next constellation, etc.

Jarad






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