Solar telescopes are used for studying the sun. They are quite large. The biggest is the McMath-Pierce Solar Telescope, with a diameter of 1.6 meters. It is housed in a structure that is 100 feet tall. 
Some new telescopes use multiple or segmented mirrors (usually hexagonal).
- New Technology Telescope (NTT)
- Multiple Mirror Telescope (MMT)
- Keck Telescope (segmented, hexagonal mirrors)