Making and using a "compound" parabolic solar cooker (Large project)

Step 2: Searching for a solution

I searched through the literature about shapes for passive reflectors and found Winston concentrators and cusp reflectors.
But the cusps did not concentrate much while the winston concentrators might be suitable for a box oven but not for what I had in mind. They concentrate in an area behind the compound parabola.
Eventually I decided that if I rotated a parabola round its focus by a certain number of degrees and joined the 2 inside curves It might work for me.
Using that shape focuses the light in an area at or below the focal point of the combined parabolas.
I have added image notes to the 2 pictures below to explain it a bit. Shape 1 is the parabola for a parabolic dish.
Shape 2 shows how to turn it to make a 45 degree compound parabolic dish (suitable for up to 3 hours of solar cooking without moving the dish!)