Comment Re:Mirrors (Score 1) 60
No, modern telescopes use mirrors instead of lenses for two reasons:
1) Once a lens gets more than about a meter across, it starts deforming measurably under its own weight (and the direction and amount of deformation changes as you shift the telescope). A mirror can be supported across its entire width and does not have this problem.
2) A lens experiences chromatic aberration, causing different frequencies of light to focus at different points. You can reduce (but not eliminate) this by using achromatic doublets or other optical tricks (such as absurdly long telescopes), or you can take the easy way out and just use a mirror.