Telescope

Telescope

Telescope

Refracting telescopes use lenses to gather and concentrate light; reflecting telescopes use mirrors to gather light and lenses to create images. No lens can bring to focus all of the colors in white light, but a mirror can. Lenses absorb some of the light that passes through, thus weakening the image; mirrors have no such problem. Lenses can be made up to about 1 m in diameter; mirrors can be made much larger and more easily. After a mirror is ground and polished to a precise concave surface, it is coated with silver or aluminum, giving it a shiny, reflective finish. Reflecting telescopes are currently used for Earth-based and space-based observatories.

This interactive explores reflecting telescopes. The large glass mirrors of modern reflectors have opened our door to the universe — and, as telescopes grow larger, the door opens wider. Learn how telescopes work and see the universe through different sized lenses.

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View Telescope