That is why I wear mine tied to the top of my ball cap...

1) this ia an old idea. They make hot dog cooks that use an elongated concave piece of polished metal.
2) Also cigarette have seen these as lighter.
3) it is what probable inspired the chocolate used to polish the bottome of a soda can.

Finally have you ever really tried to start a fire with a maganifing glass using natural material. You may get smoke but that is a long way from a flame.

cheers

There's a guy here in Humboldt who uses a big one of those to cook pots of food during the day. It works great.

It is still sporting fun to make fires in many different ways.

I'm still waiting to see how that guy could start a fire using reflected moonlight. He SAID he could show you how to do it, if only you bought his survival info.

Sue

Susan..you reflect the moonlight into your BOB so you can find the lighter and fire gel----

my first success with the fresnel lens was camping this summer - and it was very easy when I found the secret.

punky wood. I scraped some out of the south side of a standing rotting snag. got a couple handfulls. Rubbed the material in the hands to break it up. flash the lens and a small "coal" is all you need. the beauty of this material is that when you blow on the coal, it expands rather than extinguishes. Just mix in a few small twigs or birch strips and blow blow blow. soon smoke (lots) then flame. It was so simple and the key was the punky wood!

regarding the product in the post. if you are in an area like me (NH) where the sun is not so strong in the winter, you need to keep the light focused for some time to get substantial heat. this product would be much easier to "rig" in a fixed position to leave and tend to other tasks while the sun remains focused.

But the sun would be moving...

Thanks for that link. So 70 sailors, each with a 5x3ft flat copper mirror. The target was not moving, which was an advantage Archimedes would have lacked.

As I recall, Mythbusters had fewer than 20 staff, and their mirrors were smaller.

That was the problem Mythbusters had. Specifically, to aim you need feedback, which gets hard when there are lots of spots of light and you don't know which is yours. Which is interesting, but it never seemed like an insurmountable problem to me.

true, but you could adjust the focal point every few minutes or so easier than the lens. don't get me wrong, I'm just trying to see the plus side of the thing.