What is the best red LED light for Astronomy?

I am looking for a quality red LED light to save my night vision for Astronomy. Hopefully someone can recommend a light that runs on AA batteries that has a good beam and is not a cheap plastic toy.

I have no experience with it, but I believe the defacto standard is the Rigel Systems Skylite.

clik here for more info

The Palight in red led is pretty good. It has a constant-on feature so it is locatable in the dark. The low setting is functional for such tasks as astronomy or navigating around the house at night...but no more. The high output setting is fairly intense. However, the Pal operates on 9V.

One way to do it is take the PR base bulb from those cheap plastic jobs and break out all the glass envelope. Take a red LED and solder a 100 ohm 1/4 watt resistor in series with pos. lead down the center of the bulb base with the other lead soldered to the rim of the bulb base. Pot it with epoxy and you have a LED bulb that will fit any 2-AA cell light. When the cheap $1 lights give out just buy another and install your homebrewed LED bulb in it.

The CMG Infinity has a lanyard, and a clip, which will be helpful. It can run on nearly depleted batteries. The led is recessed, so it won't create a glare. The beam is beautiful, and perfectly round. It's solid (anodized aluminum), simple, waterproof. It will run for over 20 hours on one AA alkaline. You'll find other uses for it besides astronomy. You can get it for $15 from batterystation.com

I know few believe me but, being able to adjust brightness is much more important than color.

Thanks for all the ideas and recomendations. All the posts have really helped me a lot. CPF people are super ! The amount of knowledge and willingness to help others on CPF is amazing. gwbaltzell really gave me something to think about with his statement about the ability to adjust brightness with a red LED. Many times being able to adjust the brightness up or down would be a great feature in a light. Sometimes blinding brightness is not needed. I am now looking at lights that can adjust their brightness.

I borrowed a Rigel Skylite from a CPFer last summer, and put a page about it up right here if you're interested.

My 1st choice: eternaLight Ergo 3 with Red/White LED Option. Adjustable brightness, added versatility of white LEDs also, OUTRAGEOUS runtime!!!, and additional features! (They make it in a Green/White option as well.)

2nd: CMG Infinity w/Red LED

Any idea how the Ergo 3 brightness compares at the dimmest setting with the Rigel?

If you don't mind spending a bit more money, and can use CR123 batteries, you could buy the HoTech Astro Aimer. It has three bright white LEDs, a three intensity adjustable red LED, and a 5mW green laser for pointing at stars. With shipping and postage, mine cost about $239. It will also fit in the star finder one inch diameter loop and has a standard size hile for mounting on tripods.

gwbaltzell, I believe you. The dimmer the light, the less it affects night vision, but the harder it is to see anything.

It's not the light coming from the flashlight that matters, unless you look into the beam. It's the color and intensity of the light reflected from the objects you are tripping over that matters.

If the color of the object you are looking at is red, it would be seen when illuminated with a red beam but would be black when illuminated by a green beam. And vice versa. As you usually can't control the color of the objects around you, I'd think a white light has the advantage in low light conditions just as it has in more brightly lit conditions.

It's true that in low light conditions, where we see in shades of gray, not color, that our eyes are much more sensitive to green than red. All that means to me is that a properly adjusted green LED light would last much longer on a set of batteries than a properly adjusted red LED light.

On the other hand, I suppose monochromatic light focuses better on the retina that white light. If the difference is significant, then I'm wrong about the white light.

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paulr said:Any idea how the Ergo 3 brightness compares at the dimmest setting with the Rigel?

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Don't have the Rigel, though I do have a "Celestron Nightvision Flashlight"...The Celestron can be dimmed more than the Ergo 3 with Red/White LEDs.

If you want an adjustable red LED light, I suggest we get ARC to make a red ARC4

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bricksie said:
If you want an adjustable red LED light, I suggest we get ARC to make a red ARC4

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Or one of my FlexiLEDs with a RED Luxeon in it would work great since it has dimming and can run nicely on 4 AA's. See my runtime tests with a unit I built into a case for another CPFer. At dim settings you would get days of runtime.

george.

I've had a Rigel Starlight for 2 years. It has two red LEDs,no white, adjustable brightness,and a lanyard to hang around your neck. It's been great. Bright enough to light up what you need to see, and goes dim enough to not affect night vision. I don't know if they still make it,but it was under $20. You don't need white unless you're in a really dark spot.
John

I wasn't going to plug my page again. /ubbthreads/images/graemlins/banghead.gif
But I'm in full agreement that in most cases white is the best choice. The wavelength of red that is actually useful I've not seen in any premade light. And the level at which it makes any difference is so low that only under circumstances that are tightly controlled (in a dome looking for nebula) does it make any sense. Blue-green (cyan) has advantages that allow our night vision to work well but draw-backs in reading red markings and other color information. (stepping down off soapbox).

Your page is very interesting, mainly because I always thought that red light was best for maintaining your night vision. Now I don't know what to believe

Here is something I don't understand: By which light is the rhodopsin in your eyes destroyed? By every (visible) wavelength or only by some?

Rhodopsin (visual purple) is destroyed by all wavelengths (including infrared). Blue-Green (cyan) being the most effective. It is the destruction that allows us to see in low light. The chemical change is what is sensed by the rods. Each of the color cones has a similar chemical that each sense the destruction of their particular compound. This is also the cause of after images. Staring at one color will produce an after image of that colors's opposite. Actual the inability to see that color until the chemical level returns to normal. It is also this delay that poses such a problem with night vision and why vitimin A and/or beta-carotene in the diet are so important.

Also see the pinned thread in the night vision section on Human night vision preservation.

Edited to remove link to thread that no longer exists.

GWB, I'm not convinced that you have reached the correct conclusions regarding preservation of night vision.

You say "If you must see detail (reading a star chart, or instrument settings) and can lose peripheral vision (see note 1), then a very long wavelength red at a very low level. Red really only has an advantage at very low levels (were the night blind spot is very obvious)."
This seems to me to be the crux of the issue, especially for this thread, and I believe it is entirely correct.

Here is note 1 "Note: The red filtered light at the intensity most people use is likely decreasing night vision much more than a properly dimmed white or blue-green light would!".
This is a very vague and loaded statement which proves nothing.

"If you wonder why no one else has drawn these conclusions look at the dashboard of most cars. The markings are large, the pointers are large and an orange-red (a compromise, for certain "color blind" persons) and at night it is edge lit with blue-green filtered fully intensity adjustable light."
That's nice, but where is the proof that car makers have an interest in preserving your night vision? Certainly the headlights, and street lights, don't help preserve night vision. As far as I can tell, interior car lighting is primarily concerned with attractiveness and legibility, not preservation of night vision. After all, most people don't have any significant degree of night vision prior to stepping into their cars.

It appears to me that you have proven that low level red light is the best way to preserve night vision. This corresponds with my own experience that, in the dark, red light has less impact on my eyes than any other color.