Traveling at night

There have been quite a few posts involving traveling at night in a survival type of situation: flashlights, compasses, etc.

I've always considered traveling at night a bad idea. Sure, getting away from a burning plane, a dangerous animal or a high point in a thunderstorm is usually a good idea. And walking across mostly-level desert when it's cooler and you've got some moonlight, that's probably a good idea, too.

But general travel under most conditions seems kind of pointless to me. No moon, rough terrain, no trail... Wouldn't it be better to stay put and wait until you can see? I visualize myself looking at my compass and walking off a sheer drop, or walking into a feeding bear or cougar, or spraining my ankle or otherwise injuring myself.

So, what do you think? Under what conditions would you travel at night? When would you NOT even consider it?

Just curious.

Sue

well you pretty much named all situations i would travel at night. Other than direct life threathing situations and dessert temperature, i would wait till the sun comes up again.

In a desert, absolutely. In winter, with a good moon, if it wasn't terribly cold out, I would be willing if I HAD to. Gernerally, though, I start digging in about 90 minutes before dark if I'm not worried about a fire, unless I'm within 2 hours of my destination.

That is assuming that there is no pressing need to travel at night. Emergency situations might require different rules.

I think you have a point. But there are a few, rare cases where you could suddenly find yourself travelling at night, I guess. Like, if you're just out in the city after dark, and there's a power failure. Suddenly, you're out walking. At night. Or if you're in a car and it breaks down, and there's no cell coverage. You're suddenly traveling, at night. (I guess. I'd try to walk to better signal, but...) Camping, and you really have to go, you're walking at night. Didn't get back from the day hike as planned, so the sun's down but you don't have any gear to spend the night, you're probably going to keep going.

I guess what I'm saying is, people probably don't start off planning to travel over unfamiliar territory in the dark, but it can happen.

Sue,

Well, if you're in trouble and it's safe enough where you are, there's probably no good reason to travel at night.

But... I LOVE wandering at night. The world - woods, mountains, lakes, desert - is all different at night. I've been traveling at night without artificial illumination as long as I can remember. First my dad, then Boy Scouts, then the Army - heck, I don't need NVGs to own the night; I've owned it since I was a little boy. Day, night - white chocolate, dark chocolate - I like them both. Nighttime is sensually richer than daytime because vision is less dominant and my awareness of other senses expands to fill the input void.

However, I've been practicing that all my life and it does take practice. Some good instruction helps, too. And there is the matter of eye color - 1/2 our kids and I have brown-hazel eyes and we rule the night. Wife and the 2 blue eyed kids have to work a little harder when it's really dark, although they are pretty darned good with 20% or more illumination (training and practice).

Being night capable has been very important in some of my "adventures" over the years and was literally life-saving on one occasion, without question - one of those move-or-die situations. Using a flashlight probably would have injured or killed me and my dad... anyway, long story, and the short version is that it really paid to be able to move safely in terrible terrain with only low ambient light.

Our scouts have a "secret" name for themselves: "Night Hawks" - every outing includes a silent, non-illuminated night hike, just like when I was a scout. The boys rock as a group - they silently adjust for each other's inate ability and stay together nicely.

What I am getting at is that practice in traveling at night can really alter your ability to safely manage in a bad situation. Heck, it's a great help in routine situations as well. We rarely see any lights come on (and only red photons at that) if setting up camp after dark. I never need a light to find something in my pack - I know where it all is by feel. I could go on...

Practice in relatively safe terrain is good and honestly, it is a hugely enjoyable experience. If you cannot practice and gain skill, it's just as you wrote - best to stay put if feasible.

My $1.02 worth

Tom

Yeah, what he said.

However, I think that you need to have a basic familiarity with the kind of terrain you would be moving in. I'm pretty comfortable in deserty kind of country, even if it is going up and down a lot, but I would just go to ground in what folks call 'the woods.'

I agree. I hike at night, often without a flashlight. These trips are planned though and I go when the moon is full (or at least 3/4) and the sky is clear. I have also been walking out to hunting blinds in the dark since I was probably about 8 years old. With all this "experience" walking around both woods and dessert in the dark I still wouldn't travel at night in a survival situation other than under the types of circumstances you've already mentioned.

Hold on..back up a minute.

The part about eye color making a difference (quoted here:

<snip>. And there is the matter of eye color - 1/2 our kids and I have brown-hazel eyes and we rule the night. Wife and the 2 blue eyed kids have to work a little harder when it's really dark, although they are pretty darned good with 20% or more illumination (training and practice).<snip>

Are you kidding? If you're not, could you provide a link about this?

Thanks (in advance)

>> Are you kidding? If you're not, could you provide a link about this? <<

Not kidding and maybe... I might have some links buried here someplace that have that info adjunct to the main topic. I thought it was common knowledge - I believe that there is a huge body of statistical evidence on the subject but it's not a current topic of investigation as far as I know. Generalizing, the data runs from "worst" night vision at eye color blue to "best" at eye color brown. Just hearsay from me until I or someone else posts a link or two, I realize.

I don't recall reading or hearing any information on WHY - just that it is, and my own observations thru life have matched the "common knowledge".

I "can't see it" from a blue-eyed perspective, but I am certain that I can teach almost any unskilled but willing person to greatly improve their use of whatever inate night vision capability they have. Not really any secrets - before the widespread use of light amplification devices all military forces (certainly the US Army) devoted time to teaching recruits how to function effectively after dark.

What I'm geting at is that in most people I have helped "see", I can usually get a blue eyed person to see a little more effectively than an untrained brown eyed person. But not 100% - some folks just cannot see worth a hoot in low level light no matter what. In my experiences so far, all of those I've encountered were blue eyed.

There really are techniques to using the ol MK I night vision eyeballs that usually greatly improve one's ability and I suspect that most of us modern civillized folks won't stumble on them by accident - someone needs to show us.

Hope someone beats me to the punch and digs up some definite links with the info <grumble> I'd rather move on to other discussions <img src="/images/graemlins/tongue.gif" alt="" />

Tom

Well, there are two conditions under which I think night travel is ideal. One is tactical evasion, although with FLIR technology it is actually worse to be mobile and observable at night.

The second is when I am hunting or heading out to my favorite fishing hole. You gotta be up early to beat them other fellers to the bank, and if you aren't in position to take the shot well before sun up, Mr. deer will be long gone by the time you get there.

I like red LED light for traipsing at night. You don't totally destroy your night vision using that, and you aren't an obvious glowing target with them either compared to white light emitters.

In SERE, we were trained to move at night was preferable. Also, there's more critters to catch and eat on at night. Yeah, some would just as soon eat you, but generally it's the dinner bell for all predators at night. When I am in the woods, I am a predator. <img src="/images/graemlins/tongue.gif" alt="" />

Tom,

Could you amplify on your techniques for improving vision at night. I'm suspect I could improve mine (brown-eyed) a lot. That (brown-eyed) also applies to my family and most of my troop.

Thanks,

John

I recall reading that at the outset of WWII it was a common misconception among US troops that the Japanese were lousy night fighters because they were brown-eyed. That was disproved in a hurry. I think this brown vs. blue eyed business may be more myth than fact but I too would like to see hard evidence one way or another.

Regards, Vince

I agree on the myth part. Night vision depends on the retinal rods mostly so peripheral vision must be intact. The color of ones iris makes no difference.

Thinking along the lines of "improving night vision", (sensory inforamtion); I know you can improve your hearing capabilities. I wonder if you can also do this with your vision?

For those of you who, as an example, have small children that you were responsible for at night...think of how you were able to detect that child's smallest sounds...even when you were asleep.

I always thought of it as "hearing between the layers". Your brain learns to isolate the sound it needs to hear even when you are not consciously listening. I realize that a sleeping person will recognize a sound long before their vision would know start detecting anything.

Besides detecting form and movement in the dark; what other ways have any of you sharpened your night vision capabilities?

Do you depend on sounds around you as much as what you are able to see?

Naysayers: OK, I fully agree that it may be myth, but I offer a challenge: Prove it is a myth.

I "knew" this long before 1992. So far all I find on the www are statements similar to the one I made. That's not proof that it is true. But so far I find no clinical evidence one way or another.

As I wrote, my observations to date match the "common knowledge", and purposefully using night vision, purposefully teaching people to use night vision more effectively for over 30 years is at least a little bigger data set to draw on than simply guessing how well my own two eyeballs work vs someone else's eyeballs. But even that is not scientific; it's annecdotal.

Of course eye color per se has nothing to do with night vision! Is there a connection between eye color and number, distribution, efficacy, etc of rods? That is entirely possible - the question is, is it true or not in a general (meaningful) way?

I'll look for hard data because I made the statement.

But saying "it's a myth" with no supporting data is... well, prove it, OK? If we can find a truthful & definitive answer to the question, mission accomplished, whatever the answer is. I'd like to know myself - is what I said accurate or not?

I'm not flaming anyone, just pointing out that absent conclusive evidence, calling it "a myth" is the same as saying "it's true". I'm not married to the idea either way; I'd like to know the truth.

Regards,

Tom

I also agree about the myth part. In a healthy human looking at the structure of the eye (excluding the optic nerve) I can think of two factors that affect night vision capabilities:

the ratio of cone to rod cells (rod cells make you see at night). Both of which are part of the retina.

The effectiveness of the rod cells to "absorb" the light and stimulate the bipolar cells.

Other smaller factors that might be included is the distance between the rod cells and the fovea (centre of the retina where the light is focused on) and the ability of the iris to dilate, letting through more light.

Reinhardt

AyersGT,
You posted while I was typing mine therefore it's not in response to yours.

However I can see where you're coming from. That eye colour indirectly affects the ability of a person to see at night. I.e. the allele that codes for blue also affect the quantity/distribution/quantity of rod cells. Very interested in reading any evidence that comes to light for or against.

I just called an ophthamologist friend and he has never heard that either eye color has better visual acuity. Most of the websites I see say blue/green eyes have better night vision, which I do not believe either.

I looked for axactly what you were talking about: genetic cross-linkage of eye color (which is geneticly very predictable) with density of cones and/or ratio of rods vs. cones in the optic nerve array.

If it's out there, it will have to peiced together at a full-blown medical library. MedLine didn't get me anywhere.

HOWEVER: I did run onto a couple of items of interest:

http://www.nlm.nih.gov/medlineplus/drinkingwater.html

Compemndium of everything you ever wanted to know about drinkingwater. Note especially the section on "Emergency Disinfection of Drinking Water."

Poor Tom... you really know how to open a can of worms, don't ya? <img src="/images/graemlins/blush.gif" alt="" /> <img src="/images/graemlins/grin.gif" alt="" /> <img src="/images/graemlins/wink.gif" alt="" />

Troy,

Hehehe - this is more unimportant than 1095 vs 440C vs SV30 vs 357 vs 12 ga.. whatever the answer is, none of us can change our eyes out anyway, so why get excited about it in this venue? Learning to get the most out of what we have is far more relevant.

I wonder if there is a correlation between various reactions to my innocent comment and eye color.... nah, more wasted bandwidth.

Anyway, so far all I get are nothing more than what I already wrote; none make reference to specific source data. If there is a significant body of evidence, it most likely belongs to the USA DoD (could be any service, but I'll wager the Army would have had the broadest interest). I'm guessing that the data, if it exists, is in the mid-WWII to mid-VietNam date range - for what I hope are obvious reasons.

I'm going to bounce back to John and Avatar's questions and let more skilled/persistent searchers seek the truth on the matter of eye color (hope someone nails it down).

Tom

Jumping in here:

Sure, and everything I can type is readily available information and none of it is new - although it seems to be in danger of becoming forgotten information as more and more folks turn to light amplification devices - I have plenty of experience with those and they have their place. But I digress...

Caveat: Like making fire with friction, reading about "seeing in the dark" is absolutely not as good as being out in the dark with someone who can teach you.

OK - photopic, mesopic, and scotopic vision - fascinating stuff - let's call 'em "P", "M", and "S" for short.

P is daytime/ fairly high illumination and the cones do most, but not all, of the work. This is acute vision right in front of your focus. Cone = color vision and in this mode the rods main contribution is peripheral vision. You see color in front and B-W on the edges (your brain will be tricking you if you try to check this out, but you *can* prove it to yourself - no color available off on the edges - rods only come in one flavor)

S only uses the rods and they are completely absent in the center of your field of vision - that's retinal turf reserved exclusively for cones. So you have a total blind spot directly in the center of your field of vision that you use the most. Coping with that one issue effectively makes a HUGE difference for most people who feel that they simply cannot see at night. We'll come back to S in a moment.

M is relatively recently classified and explains away a few things that used to make folks like me go "Yeah, but sometimes I can see colors..." Essentially, M is a transitional mode that we use that involves enough light to stimulate the cones enough for our brains to notice but not so much that we totally overwhelm our rods. Deep twilight and early dawn are natural examples and for many of us, much more than a glimmer of moonlight on a clear night kicks this in. Without getting much into the color aspect of it, here's a simple test I use: If I can easily read a newspaper in moonlight, it's freaking bright out - for me, that's well under 50% illumination, but it varies from person to person. Proof that you are in M mode is that you can focus the print - S vision is horrible for acuity for obvious reasons. It also means that you've lost some of your dark adaptation, although it will come back more quickly once you get back into the gloom.

Bright moonlight (for me that means anything 1/4 or more) is fun while it lasts and I pay attention to moonrise/set/phase because while it knocks the snot out of my night vision, I can move through open areas as quickly as in daytime - YMMV, but it's awesome for everyone at some level of moonlight around 50% and up. OTOH, if there is a bright moon and you're mostly moving thru areas (like heavy canopy) where it's gloomy, the occasional patches of moonlight really screw you up. I have a really simple solution for dealing with that: I have an intense habit-turned-reflex to close my master eye tightly whenever light flares and only open it after the light dies out (bet you can guess where I developed that habit). One last thing - for M to really work in moonlight, you need to be in direct moonlight in all but highly reflective environments (like snow). Unlike daytime, there are pools of DARK under the trees... unless it's all snow covered and that's yet another topic in the saga (I have not found anything natural that's close to equaling snow cover, but others may know of similar environments).

See next post for more if interested.

OK - back to S: I'll hit a few things for you to work with, but there's more. Best to have a really good instructor with you, but give these a whirl: Oh - disclaimer - this has nothing to do with pilot issues (NVGs, instrument panel lights, glare, etc) - it's about being on the ground in the dark. Some of it is very relevant to being on the water after dark and some of it is true but irrelevent out on the water.

1. You cannot see anything directly in front of your field of vision. Forget it; you're totally blind there in S mode. If you're a ground-watcher when walking in the daytime, you're going to fall down a LOT walking around with S vision. Quit looking at the ground all the time.

2. You MUST look at things off-center - use the top, side, bottom of your field of vision. Around 20 degrees or a little less works best for most folks.

3. A tiny bit of light goes a long way with S - unlike cones, there are LOTS of rods feeding each optic nerve synapse - some say as many as 100 rods/nerve ending. That's a lot of additive input.

4. S is GREAT at detecting motion - it totally beats the snot out of P for motion detection. Use that. Stop, Look, Listen, smell, feel - do all that. Use the stops especially for detecting motion while you're really LISTENING - amazing what useful info you gather that way. Turn your head this way and that while you're doing this - even a nearly imperceptible breeze sounds like a gale in your ears, and it sems to automatically put the eyes into hyper-motion detecting mode.

5. CONTRAST - use the sky, use the variation between ground and trail and so on.

6. This is tricky and hard to explain/learn; it's also contradictory but true: If you stare (using the edge of your vision) at something in S mode, it washes out fairly quickly (rhodopsin, or visual purple, bleaches out FAST because it's so light sensitive). So you lose something you're intently studying... that's how a stump becomes a big fat racoon ot boogey man or - anyway, KEEP LOOKING, but ever so slightly twitch your eyes so you slightly shift the exact place the image is falling on your retina. Keep this up for more than 30 seconds and it will make you gasp - you can see the darned thing rather well! The best explanation I have heard is that our brain retains each slightly different image and uses them to build an accurate composite image. Which brings us to

7. PRACTICE - you're darned tootin' that we need to train our brains to show us what our eyes see and our optic nerve pre-processes. We get far more sensory input than we can consciously deal with and it's further complicated in S mode vision because suddenly other senses positively LEAP into the forefront, clamoring to deliver THEIR information. Don't discard that cool river of perfume running out of the short grass prarie that you just passed through, but also train your brain to better process the optic information you're getting - it is VERY different than the optic input you get almost all the time. We're clearly diurnal, but we can handle nocturnal pretty well with practice.

There is also very compelling evidence that after being in S mode for a few hours, all of a sudden our brain (or optic nerve or both) REALLY kicks in with the image processing, and the more often you use S mode the faster that kicks in. Caution: The opposite is true if you are exhausted to the point of being snoozy, at least in my experience. That's when the monsters start appearing in the darkness... shouldn't be moving then anyway, unless you're on some military marathon-death-march maneuver.

Ummm - did I mention that you simply must give yourself time to dark adapt? There are lots of techniques to help keep that time from being unbearably long, but even in the best of circumstances it takes at least 30 minutes to get to about 3/4 throttle in S mode. That's 30 minutes of no-BS DARK. If you've really been screwing your eyes up for days with bright sunlight you may be out of luck for geting anywhere better than about 10% - 25% of your basic capability working on a given night - guard your vision during the day if you know you're going to be out at night. It varies from person to person, of course.

Diet shouldn't matter for properly fed folks, but if you're vitamin A deficient, you're toast. Eat your veggies regularly - dark green leafy stuff and beta-carotine things (carrots, yellow-orange squash, etc.). But go easy on it - don't want Vit A poisoning, so just take in the normal healthy dose naturally.

A bright red light can DAZZLE you - make your pupils contract - but that will NOT wash out dark adaptation. Pupils dialate back open very quickly compared to your dark adaptation time. Rods are hyper sensitive to a short wavelength in the "green" range (around 510 nm wavelength), so if you use anything more than the faintest glimmer of green light, you will knock out your dark adaptation. There's a fine line there that I'll leave to the astronomers, who may need to use a glimmer of green for instrumental or map reasons, but for us woodshounds, stay away from anything but red. Look at a red Photon directly and you'll be dazzled. Shield it with your hand and direct the light at whatever you need to see and it will have no adverse impact.

Ach! There's more, but this post is already too long. Go practice! Walking with S mode vision fired up and humming just so totally beats the stuffing out of that little cone of light from a flashlight (torch) - you can only see where the light shines, have about nada for peripheral vision, and once you get it, you'll really HATE running into flashlight walkers. S mode gives your brain a huge panorama of visual input that you're largely unaware of during P mode vision. You can see things way off the sides... like I said, practice.

Again, remember that the words "acuity" and "scotopic" do NOT belong in the same sentance - the world is a bit fuzzy in S mode; maybe something like 20/200. And that is a good reason to wear clear eye protection if you're trudging down an overgrown gloomy path in the woods - you may very well be able to see everything quite well for your purposes, but that tiny little twig... there are techniques to spot those but that's more than I care to take on at a keyboard - best done close beside a person, pointing out things like that.

Which brings up a point - if you wear eyeglasses, they will be of comparatively little help in S mode for most folks, but they WILL protect your eye from casual twigs. If your uncorrected vision is pretty bad, leave them on even out in the open, because they will help up to a point.

Have fun <img src="/images/graemlins/cool.gif" alt="" />

Tom

Umm ... Err . .. OK .. but ... what about eye color? Curious minds and all.

And, by the way, thank you.

If you want to keep yoour night vision sharp, do not drink tonic water or drinks mixed with it.

I don't know anything more about eye color that what I already wrote, so... no one so far has turned up anything worthwhile one way or another yet on that subject. <shrug> I've been careful with avoiding the Pygmalion effect with scouts and adults and still my experiences follow that alleged fact. I searched for primary data hard enough to decide that it's either not readily available on the WWW and/or someone more skilled at searching than I will have to dig it up. All I've found is annecdotal, like my statement.

Tom

Eh? I didn't know that - the quinine in tonic water can cause slightly blurred vision and/or a temporary decrease in COLOR vision (cones; photopic vision) in SOME people (not all), which is why pilots are supposed to abstain from tonic water / quinine for 24 hours before flying, but I never heard or read anything about it affecting scotopic vision - where did you read that?

I like my occasional gin and tonic... or just plain tonic water. But I'll reconsider if it is surely known to adversely affect my night vision.

Regards,

Tom

UH, HUH. Excuses for ETOH consumption. Right.

As I understand the physiology, ETOH consumtion does not bother visual acuity, but interferes with occular movement -- hence the horizontal nystigmas[sp] test.

Well I can't find anything conclusive about eye color and night vision, but I did find this.
http://www.madsci.org/posts/archives/jul2001/994098545.Ge.r.html
This guy seems to think it is the exact opposite. I have actually heard that people with light colored eyes are more affected by bright sunlight, but I'm not sure about any of this night vision stuff.

I do know that some people seem to have poor night vision, but that is usually a cause of age. I think most people just don't know how to use their night vision because they never have had to.

This is a great topic though.

I beleive the legend about pale eyed people being more susceptable to bad things in the sun. I'm one of those 'pale eyed devils' of literature fame and I have had probelms when the brown eyed guy next to me did not.

Totally non-scentific. Anecdotal only.

Believe what you want. The burden of proof is never on someone disproving online-derived myths. The doc's response is proof enough.

Ahemm. Lawyer hat on: What, pray tell, are you talking about regarding the 'burden of proof', and what tribunal do you propose shall determine the outcome thereof?

There is no 'burden of proof' unless one agrees upon a tribunal to decide the outcome of disputes. The rules governering those tribunals are calls laws [to oversimplify].

Oh, never mind.

Insomnia can effect strange experiments at the witching hour. I have green eyes. I just put on some very strong, brown shaded sunglasses to test this brown colour theory. I walked outside and couldn't see anything. <img src="/images/graemlins/cool.gif" alt="" /> A look at how some migratory peoples travel is illuminating to both blue and brown eyed readers. Day is diurnal, night nocturnal. There are also two interphases that correspond to the sunrise and sunset hours, said terms escaping me at this hour. The old romantic irish term was called 'between the lights', refering to sun and moon when the passage between worlds is open. This also corresponds to general mischief. Many desert people will travel during these periods. The temperatures are niether to hot nor cold, there is sufficient illumination for travel, most of the night or dayshift of predators is off the clock, while many small prey animals use this brief period to migrate,drink or feed. It's a good time to observe the world in general,akin to driving into work early ahead of traffic. People in a survival situation are allready stressed physically and emotionally. Night travel should be done in small increments, letting the body's internal clock reset itself, which mine is about t..........zzzzzzzzzzzzz

And here all this time, I've been thinking that I go to bed cuz I'm tired, and I get up cuz I have to go to the bathroom.

Is that why on really stormy days up at elk camp I tend to sleep in a little longer, because it is darker out at sunrise than normal? I was kinda thinking it was cuz that warm sleeping bag was a darned sight more comfortable than traipsing up to the toidy hole with the butt flap on your longhandles waving in the breeze. I can hold my liquid a lot longer and keep my eyes shut tight when that north wind is a howling down off that ridge. Of course, there's been times when I've held on too long and there could be a tornado outside and I am still gonna have to make a run for it. <img src="/images/graemlins/shocked.gif" alt="" /> <img src="/images/graemlins/blush.gif" alt="" /> <img src="/images/graemlins/crazy.gif" alt="" />

Tom,

Thank you, as always, for the tremendously informative posts. I hope to try some of this information this weekend. It already explains why I am so good at recognizing skunks at night. I guess incentive also plays a roll in recognition. <img src="/images/graemlins/wink.gif" alt="" />

I hope you can post more of your techniques for nocturnal vision and recognition.

Thanks,

John

JShannon,

Sheesh! Getting a little warmer in here... Please carefully re-read what I wrote. Perhaps you're making a big deal out of nothing important. I asked (a little tauntingly at first, but it was meant in good humor) for assistance in finding definitive proof or disproof. I'm NOT pounding my chest about this or insisting that I'm right or you're wrong. I'm really only interested in the truth, if it is known.

Whatever you asked your optomitrist buddy generated no more proof of what you believe than what someone wrote (including me) on line about what they believe, Your post said something about "acuity", which I did not make any statement about in my original post - because I wrote about scotopic vision (comparatively fuzzy, or non-acute by geometry/biology in humans), not photopic vision - either you asked the wrong question or he/she misunderstood your question.

In any event, if the optomitrist cannot cite a study of the subject, his/her opinion is simply an opinion of one person. Has the optometrist extensive field or lab experience with subjects in the field of scotopic vision? If so, did the optomitrist notice any correlation or lack of correlation between eye color and scotopic vision ability? If so, that opinion would carry a lot weight with me, whatever the answer is.

I am not defending an unfounded position - quite the opposite; I wrote that I don't know, although I've always thought it to be true (my "myth" origin is BEFORE the WWW - my 1992 comment) . So I wrote that since I cannot show it is true, if someone feels strongly that it is untrue, please show evidence, because either way I would like to know the truth. Subsequently I wrote that my searches have turned up NOTHING and suggested that a forum member with better search skills than me would have to find "the answer".

I'm not trying to flame you and as far as I'm concerned if this post gets you all worked up, let me apologize in advance. Dead subject as far as I'm concerned unless and until someone finds a believable scientific answer.

Regards.

Tom

PS - I cannot resist asking any longer- my eye color is brown with hazel around the outer edges. Any ability I have to see in low level light is far more a product of decades of practice and learning of techniques than anything else. Would you PM me your eye color just to satisfy my curiosity? TIA.

LoL - "horizontal gaze nystagmus test" ??? Counselor, are you defending or prosecuting DUIs?

I find all the reasons I need to justify drinking by posting innocent comments here in misguided attempts to share experiences and learn new things <img src="/images/graemlins/shocked.gif" alt="" /> <img src="/images/graemlins/crazy.gif" alt="" /> <img src="/images/graemlins/wink.gif" alt="" />

Let me see if I got this correctly: If an intoxicated person stands in the woods after dark staring fixedly at something for 30 seconds or more, horizontal gaze nystagmus will kick in and help resolve a fairly high definition mental image of what he is staring at...?

<mutter> "Where IS that green bottle and do we have any limes...."

<clink!>

John,

I'd rather not, if you don't mind - it all flows out naturally in the woods and is too tedious for me to communicate effectively at a keyboard. "Tell, Show, Do" - 2/3 of that is missing on the screen.

Anyway, how about *I* get to learn some new tricks - there must be many here who are night owls and I bet I could learn some useful new things if THEY would share... I expect that in the next 10 years or so my night vision will decline significantly, so I'll need to learn more or else slow down a lot (that would really suck).

How's the Eagle doing?

Regards,

Tom

Tom,

You gotta quit being so provocative! ROTFLMAO Just do what I do....ER... Don't do what I do, but ....Well just do it right next time. I hope that helps. I do believe that some of our forumites have become a little cranky lately.

No problem re further techniques. I guess some things are better learned in person than by reading. I'll see if I can find somebody who's nocturnal. Oh, you mean me. Well I guess I do qualify. Unfortunately my late surfing hours tend to follow my late research and writing projects. That's when my brains are most fried. Anyway I usually get in a nightly walk, but it tends to be suburban with a lot of light pollution to impede the development of any real night vision. Weekends are my best chance for developing some useful night vision. I'll see what I can do.

My Eagle-to-be? He's stalled. He's been working 7:30 a.m. to 9:30 as a counselor and lifeguard at nearby BSA camp. He loves that, but it hasn't left him a lot of free time. This Saturday morning, after finishing Webelos camp, he went on a boating trip with the other camp staff. Next Friday he starts a week's training in leadership in Oak Badge. In mid-August he'll finish his paperwork, we hope. He actually doesn't seem to have that much left to do, but still he needs to do it himself. I guess in assembling his book, Mom can [i.e., will need to] help.

Best wishes and God bless,

John

Tom, let me share a bit of technology for what I think might be the ultimate low-dazzle, low-power, home built, functional but kludge looking red light. I saw the basics of this guy over at Candelpower, IIRC, but I've modified it since.

You will need:
1x MagLite Solitaire
1x 3mm red LED from RadioShak's assortment pack
1x #4 spring from your local hardware store's spring box
1x small bolt or other metal spacer
1x MN/21 battery (Walmart has a two pack of Duracells for about 80 cents; I've only done this with Duracells, I can't comment on other brands!)
1x pair needle nose pliers or very small hemostats
1x pair wirecutters, diagnal or end

Strip the Solitaire, set the bulb aside for latter. I keep the one in the endcap there, so I can go back to normal lighting with a scrounged AAA.

CAREFULLY bend the leads of the LED to match those of the bulb, then trim the leads to the same length. Examine the bends- if you can visably see any kind of crack or gap or pit in the bends, discard it and try again. If you use that, the lead will break off while you are pulling it out for whatever reason, and then you get to ffigure out how to detail strip a Solitaire to get it out again.

Use gentle pressure to push the LED into the bulb socket. You will feel a little bit of resistance- you are literally forcing a square pegs into a round hole. :P Don't worry, it only effects the soft plastic, not the metal, and when you go back to a normal bulb, it will be held just as tightly as before. I think what is happenening is that it is scoring the circles, but they are still there.

Screw the lens assembly back into place. You will have a small (~1mm) gap, but it won't effect water resistance in the least.

Now we start to really make the product liability guys flinch. <img src="/images/graemlins/smile.gif" alt="" />

Using the pliers, CAREFULLY take the skin of the MN/21. Inside you will find 8 coin batteries. You will want 3 of them. line up thier polarity and carefully drop them into the light. Put in the spring and the spacer. Replace the endcap.

(For those that are interested, each one of these is a 1.5v, 200mA supply. They are marked as LR932, which when I priced them by themselves, were a lot more expensive.)

If the light doesn't light, the batteries are on in backwards.

You will get a very faint red glow from of three of these cells. It is so faint, in caft, that it is really only useable when your eyes are dark adapted. The LED will last just about forever, and three batteries are good for a long time, at least 6 hours, but I've never sat down and timed it. If you need more illumination, take out the spacer, and drop in a fourth battery, then puth the spacer back in. In this configuration, the LED is still not as bright as a red Photon, but it is usable.

Total cost, including a new Solitaire, is about 12 bucks. As I mentioned, carry a regular bulb (and you can acutally get TWO into that endcap), and all you need to do is scrounge a AAA to go back to normal.

If you buy the assortment pack, you also get green and yellow LEDs. The greens seem to have very delicate leads, I can only bend about half of them into place without breaking them. The yellows are just fine, but when I tried this mod on a minimag, they all smoked on a pair of AAs, so I think this will be pushing the limits of thier performance. Don't be suprised if they die on you. This works fine with generally available 3mm(T1) red LEDs from a number of vendors, I just suggest the RS becuase it is easily available to everyone. I have yet to try blue or white LEDs but it should work.


BTW, while you are in the spring bin, grab some #3s. They are better than the ones that come with the MiniMag. You need to shave down the bulb holder (or discard it, and just carry the bulb in a bit of unshrunk heatshrink), and stick the spring down into the bulbwell. Much harder to loose, and much more possitive pressure.

Ironsraven,

Cool idea, making a low intensity red - thanks. There's an unused Solitaire in the log base here somewhere... anyway, your idea gives me another idea along those lines (low intensity red).

I can offer you a tip about the smoked yellow LED: You need a resistor in the circuit. Coin cell batteries like you got from the little 12v MN21 work OK without a limiting resistor because as soon as the LED tries to draw enough current to fry itself, the internal resistance of the battery shoots up - they cannot deliver much current. But AA batteries have the capability to deliver far more current than it takes to fry a 5mm LED. Check the specs on that yellow LED and you'll see it probably has a rated Vf of 2.xxx volts. Two AA in series give you ~3 volts. And the LED has a max rated current - probably about 20ma or maybe 30ma if it's a super bright.

Really really simple math to figure out what size resistor to stick in there and if you do it using an insulating disk to hold the resistor between the batteries (or between the battery stack and either end), it's trivial to pull the resistor and LED and then drop the bulb back in. A resistor automatically means that your circuit efficiency is reduced because you're bleeding some power into heat, but over-all it's a tiny amount of power anyway, so run-time should be really generous - I'm guessing well over 100 hours on two AA - maybe far more than that. Rather than re-hash all the how-to, there's plenty of help on this on the 'net (or surf CPF). Even on and off-line calculators for this.

You might get away with a green in the 2 x AA because IIRC, they want something in the neighborhood of 3.6 volts - anyway, over 3 volts. So it might light up VERY faintly, with extremely low current draw, direct-connecting it to two AA in series - have not tried it myself, but it may work. A 5mm would give a little more light, but you would have to mod either the reflector or the LED package to fit it in a minimag.

Thanks for the low-intensity red idea!

Tom

Those are both really cool ideas. I think I have a Mag Solitaire laying around here too somewhere.

The desert is surely a place for night travel in the summer, if you must walk somewhere. Seeing is not always that hard, once your eyes adjust to the dark.
It was pretty common in the military to have to move at night, without night vision equipment. Tactically, it is safer although night vision, FLIR and thermal imaging make it less desireable. One thing to consider is that few soldiers have night vision equipment, often do not use it on the move because of depth perception problems and some sensors can be overcome by resoucefulness. We once hid successfully from an AC-130 gunship while on a training mission. It did not take much. However, as the AC-130 crew said later, if we had fired on you, even though we did not see you, you would likely gotten up and ran!
Anyway, night travel may not always be desired but in an emergency may be a necessity. Having a good light source and navigation aids, along with the ability to travel in darkness, is a good skill to aquire.

That's the problem with radioshak components- no data sheets. I didn't feel like trying to figure out a big enough digikey or jameco order to make it worth while. Still haven't, that's why I have tried this trick with a better LED. I'm sure I could go and snitch one from the supply closet, but why bother? I really wanted it for the red any way.

I was pretty sure that it was a question of amperage. I'm just not ambitious enough on this project to figure out what size of a resistor I need in the circuit *humming nursery rhymes* Twinkle, twinkle, little star, power equals eye-squared are. :P

I have heard the same thing about night vision and eye color. I have read some on the subject in anatomy class. I look for my notes.

Just a shot in the dark, but typical data for a TRS 3mm Red looks like 2.25v - 2.6v at 28ma max. Feeding it 3v, try a 33 ohm 1/8 watt resistor. For a 5mm yellow run-of-the-mill, 2.15v to 2.6v Imax 36ma - try a 22 ohm 1/8 watt resistor. I figured them at 2.3v across the LED and 25 ma for red and 35 ma yellow, closest standard resistors, and 1/8 watt is the standard little TRS resistor power rating, which is more than large enough. You can fiddle with the numbers - here is a link to a calculator. I think I was wrong about the green LED Vf - looks like most of them are in the range of the red and yellow and the cheapies take VERY little amperage.

HTH,

Tom

Caleb,

Thanks - whatever you find, please let us know. It would be very cool if you had a source data cite, but some info beats none.

Regards,

Tom

From what I can recall the color of the eye has little if any effect on you ability to see at night. The correlation is dark eyed people happen to have more rods (light sensitive part) than light eyed people. Light eye people have more cones (color sensitive part) than Dark eyed people. In a nut shell Dark eyes usually indicates better night vision. Light eye indicates better color distinction. None of this is absolute there are light eyes with great night vision and dark eyes with great color distinction. And there are the super freaks with great eyes altogether. <img src="/images/graemlins/shocked.gif" alt="" />

P.S. Let me know if you have any questions or conflicting information.

Or you could just buy a Gerber Infinity in red.

-john

Two reasons why I'll pass on the offer:

1) This can be converted to run a white incancent bulb in about 2 minutes if you have a spare AAA in your kit. By the same token, if you want to boost the output level, put in an extra battery over the three I mentioned. And you can change colors pretty easily. (ok, that is 1a, 1b, 1c)

2) Solitaire $5
enough batteies for 4 changes <@2
spring ~25 cents
small steel bolt free, easily scrounged
LED about 60 cents through RS
(ouch- you can find them as low a cent in bulk packs)

Less than half the cost. About the cost of the S&H. For Scouts, that is a big facotr. It is also a good project to show kids how to build and modify thier gear better suit thier needs.

Then I've got a good one in there. I'm feeding it 6 volts/200mA with the normal load, 4.5V with the glow mode. I've red through a 3 hour bloackout with it, that was the longest burn. I was expecting it to go into thermal runaway, actually, becuase it was starting to get warm, so I left it on for an hour and it still runs fine. Still using the origional LED and the origional cells after about a year.

I haven't breadboarded it yet measure each point. Maybe I will do that this weekend. (Yes, I freely admit to having to get an unlife, before I get a life. :P )

I thought about putting in a resistor and just uising an unskinned MN/21, but since this method works well enough, I'm reluctant to fiddle with it. One thing I thought about was a drop in capacitor module to turn this guy into a microstrobe if needed.

And just realise I said resistor, when looking to drop current in the post before this. *bangs head, chanting "voltage drop"* been a while since I took DC circuits.