A parabolic reflector mirror, made of the stuff that is inside those tubular skylights, about 9 square feet, with a turning metal base, focused out to a platform where a big pot of pot roast was cooking. $589. Didn't get the brand name. Sure was working good, though. But one would have to sit there and tend it and move the thing as the day wore on. Looked like it worked good, though. Wouldn't be hard to build, either.