These are photos of my twin steel bowl cooker late in the afternoon. I tip the bowls forward to capture more sun.
I have been trying to make the bowls, reflector assembly 'as bright as possible' when trying to focus the cooker to maximize the heat capturing potential.
To make sure the cooking vesel and glazing bowl are in sun, I look for a reflection of the reflector on the glass lid used for glazing.
Today, I took small bowls of navy beans straight from the freezer and in 3 hours the beans were ready to eat.