Night vision

Could be a "rage" but I meant a "RANGE".

You know when you're out bush and you hear some ruffling in the trees. I'm always wondering what it is. One could say it's a drop bear? Would really just be entertainment purposes.

Looking at nightvision.com.au and you see the binoculars are all about $1000 or more. Except for one that is about 3rd of the price, so you have to wonder why that one would be so cheap.

I reckon you're right though...u get what you pay for.

I'll give that one a miss thanks.

see with your ears, if it bounces and crashes its a wallaby or roo, if it hoots its an owl, if you hear a small squeak and then a minute later a crushing sound then it is the red belly outside your tent eating a bush mouse or rat. (at meroo snakes have learnt that people drop food scraps near tent and that the mice/rats will go there when it is dark :)

Full Moon is the best night vision, and you could also use a torch.

try red celaphane over the torch

thanks for the tip - I will store it in my memory bank, next time we are in the ES I will give it a go

Sue

don't bother. Red light travels the least distance; that is why military use it in comms rooms, reading maps etc. There is no cheap alternative to night vision; either spend the money on the real thing or use a white light torch.

Gossy,

I am curious to know why / how red light travels the least distance. I am not sure what that means.

I don't know the 'science' behind it. We just learnt that in the military. That's why control rooms on Navy boats/ships have red light during operational activities, comms rooms have red globes installed for the same reason. Reading maps out bush are only done under cover with a red torch.

http://en.wikipedia.org/wiki/Night_vision

In biological night vision, molecules of rhodopsin in the rods of the eye undergo a change in shape as they absorb light. Rhodopsin is the chemical that allows night-vision, and is extremely sensitive to light. Exposed to a spectrum of light, the pigment immediately bleaches, and it takes about 30 minutes to regenerate fully, but most of the adaptation occurs within the first five or ten minutes in the dark.

>>> Rhodopsin in the human rods is less sensitive to the longer red wavelengths of light, so many people use red light to help preserve night vision

as it only slowly depletes the eye's rhodopsin stores in the rods and instead is viewed by the cones.

Yes, I was aware that using red light preserves your night vision, but I was intrigued as to how red light travels a lesser distnace than other visible light. Afterall, all electromagnetic radiation (including visble light) travels at the same speed and the visible the spectrum would not be partially filtered our by our air. Red dwarfs, which can be thousands of light years away, produce red light which still manages to reach us. Hence my question.

I can understand why map reading rooms out bush, at night would use red light but, as I have never been on a ship, I don't understand why on ships. Is it only at night or all the time?

Folks, no offence but we have got off track to the question posted by Ian and Sue.

Never thought to look on ebay. Thanks.