Primary mirror

One of the first known reflecting telescopes, Newton's reflector of 1668, used a 3.3 cm polished metal primary mirror.

For example, the Giant Magellan Telescope will have seven 8.4 meter primary mirrors, with the resolving power equivalent to a 24.5 m (80.4 ft) optical aperture.

The Hubble Space Telescope has a 2.4 metres (7 feet 10 inches) primary mirror.

[5][6] The Green Bank Telescope has the world's largest steerable single radio dish with 100 m in diameter.

[7] There are larger radio arrays, composed of multiple dishes which have better image resolution but less sensitivity.

Six of the 18 primary mirrors of the James Webb Space Telescope being prepared for acceptance testing .
The correctly ground backup primary mirror built by Eastman Kodak for the Hubble space telescope (the mirror was never coated with a reflective surface, hence its honeycomb support structure is visible). It now resides in the National Air and Space Museum in Washington, DC. [ 1 ]
The largest non-segmented mirror in an optical telescope in 2009, one of the Large Binocular Telescope's two mirrors.