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Hans Lippershey
Lippershey tried to lay claim on a device with three times magnification. His telescope had a concave eyepiece aligned with a convex objective lens. -
Thomas Harriot
The British ethnographer and mathematician Thomas Harriot also used a spyglass to observe the moon. -
Marin Mersenne
Marin Mersenne proposed a telescope consisting of a paraboloidal primary mirror and a paraboloidal secondary mirror bouncing the image through a hole in the primary, solving the problem of viewing the image. -
James Gregory
. James Gregory went into further detail in his book Optica Promota, pointing out that a reflecting telescope with a mirror that was shaped like the part of a conic section, would correct spherical aberration as well as the chromatic aberration seen in refractors. -
Johannes Kepler
Johannes Kepler studied the optics and designed a telescope with two convex lenses, which made the images appear upside down. Working from Kepler's writings, Isaac Newton reasoned it was better to make a telescope out of mirrors rather than lenses and built his famous reflecting telescope in 1668. -
James Short
- The British mathematician, optician James Short began experimenting with building telescopes based on Gregory's designs in the 1730s. He first tried making his mirrors out of glass as suggested by Gregory, but he later switched to speculum metal mirrors creating Gregorian telescopes with original designers’ parabolic and elliptic figures.
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William Herschel
William Herschel began to occupy his hours with the construction of reflector telescope mirrors. In 1778, he selected a 6 1⁄4-inch (16 cm) reflector mirror and with it, built a 7-foot (2.1 m) focal length telescope. In 1783, Herschel completed a reflector of approximately 18 inches (46 cm) in diameter and 20 ft (6.1 m) focal length. He replaced the mirrors several times. In 1789 Herschel finished building his largest reflecting telescope. -
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Karl August von Steinheil and Léon Foucault
Karl August von Steinheil and Léon Foucault introduced a process of depositing a layer of silver on glass telescope mirrors. The silver layer was not only much more reflective and longer lasting than the finish on speculum mirrors, it had the advantage of being able to be removed and re-deposited without changing the shape of the glass substrate. -
Radio astronomy
Karl Jansky discovered that the Milky Way was a source of radio emission while doing research on terrestrial static with a direction antenna. Building on Jansky's work, Grote Reber built a more sophisticated purpose-built radio telescope in 1937, with a 31.4-foot (9.6 m) dish; using this, he discovered various unexplained radio sources in the sky. -
Ultraviolet telescopes
- Although optical telescopes can image the near ultraviolet, the ozone layer in the stratosphere absorbs ultraviolet radiation shorter than 300 nm so most ultra-violet astronomy is conducted with satellites. Ultraviolet telescopes resemble optical telescopes, but conventional aluminium-coated mirrors cannot be used and alternative coatings such as magnesium fluoride or lithium fluoride are used instead.
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Active optics and adaptive optics.
the introduction of two new technologies for building larger telescopes and improving image quality, known as active optics and adaptive optics. In active optics, an image analyser senses the aberrations of a star image a few times per minute, and a computer adjusts many support forces on the primary mirror and the location of the secondary mirror to maintain the optics in optimal shape and alignment.
