Any introduction to astronomy textbook will help you out. I used BOB.

Instead of having huge individual telescopes which run into issues {How do you keep the mirror clean? What shape do you make it? How do you deal with the atmosphere (Adaptive optics are hard enough for small telescopes)? Constructing a telescope this large in space would be fantastically difficult and expensive.}, you can do interferometry. The largest telescopes these days run into the tens of meters, see E-ELT.