The comment above is deceptive. It's technically correct, because the sensor is capturing data from a reflection of a curved mirror. IIRC it's actually two reflections, so the imaging device is facing forward still. This is how most telescopes work though. In the same way, it's accurate to say "this is how mirrors work" but that doesn't sound impressive. It's just a reflection.

Oh, I was just joking. But the answer to your question, from what I remember from physics, amounts to lenses focusing and refocusing and concentrating light until the physical limitations of light, with reference to concentration and uncertainty, can no longer be reconciled into a cohesive picture.

To explain, light pushes away light of other frequencies fairly hard, which means taking in the whole picture at infinite distance is essentially impossible. The light’s been pushed for too long, too randomly! It’s basically a lumen mosh pit, out there. It’s quite blurry, if you attempt to do so. Like putting on someone else’s glasses. While you can’t take in the whole picture from infinite distance, you can still do so from pretty far, which is what Hubble does.

Modern telescopes, unlike Hubble, generally don’t use waves like visible light. To expand a smidge more, visible light readily interacts with most matter and energy, so modern telescopes instead use far longer waves like radio waves to take in the lay of the universe. Radio waves are too long to be majorly altered by their surroundings. Still not useful for infinite distance, but good for orders of magnitude greater distance, which is good enough.

But some modern telescopes do use visible light, and they function on principles that I’m utterly unqualified to even speculate on, for I am not a physicist.

I also can’t be trusted to explain lenses without confusing you, and for that I apologize. That’s entirely on me