Low low

LED Flashlights – General Info
1

I need some advice.

I want a low-low flashlight to use when operating a telescope. I have a reasonably bright telescope (200mm f5 ) and I like the brightest objects so my night vision is never fully adapted.

This being the case, I can use some extra light. As of now I use an akoray k106 as low as I can get with some paper and a coca cola bottle cap (red-ish) in front. This setup put out a very low diffuse light, but there is a red ring in my field of vision..

Is there any flashlight that can go this low, and still have a reasonable (let's say 50 lumens) high ??

2

Use a red LED. Driven at a few microamps. Red light will keep your night vision working. If it does five lumens it is far too bright.

Attach the cheapest red LED you can find to a CR2032 cell. If those cells are expensive in Brazil PM me your address and I'll post 5 of them to you.

I regard the moon as light pollution...

3

As usual, that's excellent advice. In the military, we make use of red and green lights in low light settings where natural night vision preservation is a concern. The specifics aren't really all that relevant to your situation since you're in a controlled environment. In a nutshell, I can tell you from personal experience that low output red and green light work really well, as long as you can control outside factors. As for wavelenths, I'm not even remotely qualified to make any educated statements. Sorry. One thing I do have some personal experience with is the K2s DX sells (WF-501B host, you should be able to find them if you search for "Luxeon"). With mil-spec NV equipment they are way, way, way too bright to be even close to useful (the issue is obviously academic but those lights are blindly bright and also seem to emit all kinds of funky wave-length voodoo light when viewed through nights).

If I were you, I'd go with red or greens. Just be advised that purpose-built equipment tends to be very expensive (smallish lights are usually meant to be weapon-mounted and thus expensive).

4

CR2032 are expensive here, but I have a few from DX. The problem is that the LEDs I have are still too bright when directly attached to a fresh CR2032. The best result so far was a LED attached to 2 almost discharged LR932.

I'll buy cheaper ones and give them a try.

Is there any disc shaped resistors? The pressure sensitive material from the other post comes to mind. A pressure sensitive fauxton, now that's an idea....

5

Now that's an interesting idea. Where did I put that bag of white LEDs?

6

Maybe you can fiddle with a 2usd DX 2xAAA red laser pointer and mod the head with proper light dampener. Since it s pretty focused you can easily "regulate" how much light you want to escape by obstructing the light escape path. The onlly issue would be to find a way to switch it on without keeping pressed the damn button. Runtimes however can be short... Most can be pot modded and in your case find a setting that just barely light that thing up.

I tought of this because astronomy afficionados are often associated with laser pointers any you might already have one.

7

1 - Buy a cheaper LED;

2 - I'm pretty sure Don will build a pressure sensitive fauxtom - wait for that;

3 - Buy a new laser.

I have a green 50mv astronomy laser. Pretty useful to point to a star (clearly visible beam at night), but will mess your night vision if it hits something....

Wish list - disc shaped resitor that I could use to build very low fauxtons...

8

I've made a ramping fauxton. The QTC material is about the same thickness as a CR2016. Thse things will work on one CR2016, so I replaced one of the cells with a small square of QTC. Problems is, it is not all that easy to keep a constant finger pressure. I think a certain amount of messing with it is called for.

The black speck under the LED leg is a pill of the compound.

9

That is ultra cool!