The larger solar parabolic trough on the left I made in the 1970s for the New England Coastal Power Show, an energy show which traveled throughout the Northeast for a few years after the second Energy Crisis. We used it to heat water, make tea, and demonstrate the availability of solar energy as well as many other working alternatives to nuclear power.
The smaller solar parabolic trough on the right is a solar oven now available from GoSun (https://gosun.co/
) which has been making solar cookers for many years. You can put it together and take it apart in a minute or two. The collector has something I imagined back in the day but never built, a sealed insulated dark absorber to maximize solar heat collection.
I may modify the little GoSun trough so that it can also be a vertical collector like my older model. The sealed absorber looks like it could boil water just as well as if not better than my old copper one.