Homemade incinerator beam!

[geoschmo]

Figure a steak the size of one of your mirrors is getting enough energy to raise it's teperature to 90+ degrees on a hot day. You only need it up to 200-300 or so to cook it. You could do it with 3 or 4 of your mirrors there. You wouldn't need or want to focus them as precisecly as you are doing there of course. You want the focal area of the reflected light about the same size as what you are cooking instead of down to a point like you are doing when burning sticks.