primary mirror

British  

noun

1. the mirror that collects and focuses the incoming light in a reflecting telescope

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Example Sentences

The primary mirror, M1, is the largest mirror ever made for an optical telescope.

From BBC

Webb used its huge 6.5m-wide primary mirror and sensitive infrared instruments to make the discovery.

From BBC

By combining the four VLT 8.2-metre telescopes at ESO's Paranal Observatory, they can resolve details as if astronomers would employ a telescope with a primary mirror of 200 metres in diameter.

From Science Daily

Each of them stands out from objects far more distant via its very sharp, pointlike appearance, as well as the presence of diffraction spikes—three pairs of lines that radiate away from a star’s center and are caused by the bending of light around the hexagonal one-meter mirror segments that make up JWST’s primary mirror.

From Scientific American

It's not just the sharpness of image that Webb can achieve with its 6.5m primary mirror, it's also the breadth of colour its instruments can now detect that makes the telescope so special.

From BBC