Simple telescope design question

Chris Rowland wrote:

There are things called Tilted Component Telescopes (TCT), aka
Trischifspieger, Yolo and so on that have three curved, tilted
surfaces where the abberations produced by the tilts cancel out. A
Google search on some of these terms will come up with some really
strange boxes containing scopes. They avoid the problems with the
spider and central obstruction but at a cost in size and complexity.

Not to mention accumulated errors and scattering. An off-axis paraboloid
is a much better solution. See for example
http://users.erols.com/dgmoptics/ This is popular only recently when
relatively cheap automated production of large "parent" mirrors became
possible.