I make use of the concave form in my reflector telescopes, one Newtonian, the other Maksutov Cassegrain.

The concave form is a wonderful thing.

Your comment is interesting because the task of designing telescopes calculates the concave form from the side view, not from the focal point. How do you use your telescope? Where is the audience?

I use them to view the moon, the sun, the planets, galaxies, star clusters, nebulae, binary stars............. and I sometimes take pictures but I'm still honing my skills in that area.

My audience is on FaceBook.

Are you referring to the way in which the concave form takes the diffuse and faint and focuses into something with far more impact? Sort of like standing under a dome and clapping your hands can be deafening, but out in the open, it quickly fades? Or how it can take light and focus it into a point hot enough to set fire? Or the way skilled propagandists can coalesce random and individual, yet widespread discontent into a powerful movement?