Anatomy of a Radio Telescope

The basic anatomy of a radio telescope hasn't changed all that much from Reber's dish—though the instruments have become much larger and the electronics more sophisticated. A radio telescope works just like an optical telescope. It is just a "bucket" that collects radio frequency waves, and focuses them on a detector. A large metal dish—like a giant TV satellite dish—is supported on a move-able mount (either equatorial or altazimuth). A detector, called a receiver horn, is mounted on legs above the dish (prime focus) or below the surface of the dish (Cassegrain focus). The telescope is pointed toward the radio source, and its huge dish collects the radio waves and focuses them on the receiver, which amplifies the signal and sends it to a computer. Since the radio spectrum is so broad, astronomers have to decide which portion of the radio spectrum they will observe. Different receivers are used for observations at different frequencies. Receivers are either swapped in and out, or (more typically) the radio signal is directed to the correct receiver by moving a secondary reflecting surface (like the secondary mirror in an optical telescope).

Astronomer's Notebook

Why do radio telescopes have to be so big? A 30-foot dish seems excessive. The resolution is actually determined by the ratio of the wavelength being observed to the diameter of the telescope. So optical telescopes (which detect short-wavelength optical photons) can be much smaller than radio telescopes, which are trying to detect long-wavelength radio waves, and have the same resolution.

Telescopes Mastery

Telescopes Mastery

Through this ebook, you are going to learn what you will need to know all about the telescopes that can provide a fun and rewarding hobby for you and your family!

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