Commonly Asked Questions in Physics by Andrew Rex

Author:Andrew Rex [Andrew Rex]
Language: eng
Format: epub
Tags: Math & Science
Publisher: CRC Press
Published: 2014-02-11T16:00:00+00:00

Schematic diagram of a reflecting telescope.

What Are Some Novel Designs for Modern Reflecting Telescopes?

Astronomers started building very large reflecting telescopes for research in the early twentieth century. Edwin Hubble used 100- and 200-inch (referring to the diameter of the reflecting mirror) telescopes to do his pioneering work on distant galaxies, and that work led to our present understanding of the origins and expansion of our universe. You don’t have to worry as much about a reflecting mirror’s weight because it sits at the bottom of the telescope, compared with a refracting telescope’s objective lens, which sits at the top. Even so, it’s difficult to keep a very large mirror from sagging under its own weight. Any deviations from a perfect parabolic shape in the reflecting surface produce imperfections in the telescope’s images. For that reason some modern telescopes use a segmented primary mirror made of many smaller pieces that are easier to manage. The two Keck telescopes in Hawaii use segmented mirrors that contribute to an overall reflecting diameter of 10 m, with the segments computer-adjusted to maintain the proper curve as atmospheric conditions change.

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