why are all telescopes round?

Why do scopes always have a round mirror, wud it make a difference if it was square?
thanks

Fionn,
I think that's such a great question. Someone thinking outside the box. Sometimes we can get so taken up with the details that we miss the big picture. It's fun watching people trying to develop an answer/explanation.

Cheers,

From a production point of view I'd say it's a cost factor. For years we've been producing spherical based optics and cylindrical tubes. Always cheaper to stick with what you know best!
There's also great inherent strength in a sphere/cylinder construction. Items are also easier to clean when there are no corners.