ELTs
The top three ELTs that are funded with two smaller but completed large telescopes for comparison (background yellow). In the early 2000s, all three targeted completion in 2018, although this slipped to 2022 for one.
| Name | Image | aperture (m) | Equiv. ap. area | Area (m²) | M1 Mirror segments | Note | Altitude | ~ Cost |
|---|---|---|---|---|---|---|---|---|
| European Extremely Large Telescope (E-ELT) |
39.3 | 39.3 | 978 m² | 798 × 1.45 m hexagonal (f/1) | Site chosen: Cerro Armazones, Chile | 3060 m | €1.055 billion | |
| Thirty Meter Telescope (TMT) | 30 | 30 | 655 m² | 492 × 1.45 hexagonal (f/1) | Site chosen: Mauna Kea, Hawaii | 4050 m | $1.2 billion | |
| Giant Magellan Telescope (GMT) | 24.5 | 21.4 | 368 m² | 7 × 8.4 m circular (f/0.71) | Site chosen: Las Campanas, Chile; 2 mirrors cast (2/7 M1), 1 polished | 2516 m | $700 million | |
| Large Binocular Telescope (LBT) | 22.8* | 11.7 | 111 m² | 2 × 8.4 m circular | Largest Binocular; largest non-segmented mirrors; First bino-light 2008 | 3221 m | $120 million | |
| Gran Telescopio Canarias (GTC) | 10.4 | 10.4 | 74 m² | 36 × 1.9 m hexagonal | Largest single mirror; Fully Operational 2009 | 2275 m | €130 million |
*The LBT telescope baseline is via aperture synthesis.
The Very Large Telescope is also of note, with 4 × 8.2 m, 4 × 1.8, and 1 × 2.61, all on separate mounts but in one building for Interferometry.
Read more about this topic: Extremely Large Telescope