461 First Reflecting Telescope

English physicist Isaac Newton built the first reflecting telescope in 1668. Newton’s idea for a reflecting telescope was not new. Galileo Galilei and Giovanni Francesco Sagredo had discussed using a mirror as the image forming objective soon after the invention of the refracting telescope, and others, such as Niccolò Zucchi, claimed to have experimented with […]

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462 Aberration of Starlight

By the 18th century, all astronomers believed that Earth revolved around the Sun, and not vice versa, but they had no direct observational proof. English astronomer James Bradley provided confirmation in 1729 when he discovered the aberration of starlight. Essentially, he found that an observer has to point his or her telescope slightly in the […]

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464 200-inch Hale Telescope

  On January 26, 1949, the 200-inch Hale Telescope at Palomar Observatory in California collected its first light from a celestial object—Hubble’s Variable Nebula (NGC 2261). The instrument’s construction had begun in 1934, but interruptions from World War II delayed its completion. The primary optic in the Hale Telescope was the first large mirror made […]

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471 Energy Collected by Radio Telescopes

A radio telescope is a specialized antenna and radio receiver used to receive radio waves from astronomical radio sources in the sky in radio astronomy. Radio telescopes are the main observing instrument used in radio astronomy, which studies the radio frequency portion of the electromagnetic spectrum emitted by astronomical objects, just as optical telescopes are […]

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