I am with the walrus also.
I do have a question.
With the best lens humans can make today, what is the percentage of energy of the square foot of sun that is actually being concentrated?
As a kid, I used a fair dinkium sized magnifying glass to burn/blow up stuff and I know I was not using the total surface of the sun.
Sun rays are parallel as far as is practical for us so, with loss caused by the atmosphere, is not what I am using just a percentage of the power in that small diameter? :dubious:
With a 10 sq in glass, I am getting only a percentage of the power that the glass can see/utilize and then the losses of the imperfect glass get added, so do I have enough power on a spot 1/10th of a square inch, to get the target over the point source temperature of the sun?
Not what the OP really asked but I was wondering how hot the spot I made as a kid in the instant of maximum temperature?