Summary of the development of the telescope

• Early 13th century: Italian monks and scholars experimented with glass lenses to magnify text.

• 1608: Hans Lippershey, a Dutch eyeglass maker, created the first refracting telescope using two lenses.

• 1609: Galileo Galilei improved the design, making telescopes with up to 30x magnification for astronomical observations.

• 1611: Johannes Kepler suggested using two convex lenses, enhancing image quality in refracting telescopes.

• 1668: Isaac Newton invented the reflecting telescope, using mirrors instead of lenses to avoid chromatic aberration.

• 18th century: Reflectors grew larger, with William Herschel building a 40-foot-long telescope by 1789.

• 19th century: Achromatic lenses, developed by Chester Moor Hall and John Dollond, reduced colour distortion in refractors.

• 1840s: Photography paired with telescopes, enabling permanent records of celestial objects.

• 1897: The Yerkes Observatory’s 40-inch refractor became the largest working refracting telescope.

• 1917: The 100-inch Hooker Telescope at Mount Wilson marked a leap in reflector size and power.

• 1930s: Radio telescopes emerged, with Karl Jansky detecting cosmic radio waves.

• 1940s-50s: Larger reflectors like the 200-inch Hale Telescope at Palomar improved light-gathering capability.

• 1960s: Adaptive optics began correcting atmospheric distortion in real-time.

• 1990: The Hubble Space Telescope launched, offering unprecedented views from space.

• 2000s: Segmented mirrors, as in the Keck Observatory’s 10-meter telescopes, pushed size limits.

• 2010s: The James Webb Space Telescope (launched 2021) used infrared to peer deeper into the universe.

• Today: Giant projects like the Extremely Large Telescope (39-meter mirror) aim to explore exoplanets and dark energy.

 Definitions:

• Refractor: A telescope that uses lenses to bend and focus light to form an image.

• Convex lens: A lens thicker in the middle than at the edges, curving outward to converge light rays.

• Chromatic aberration: A distortion where a lens fails to focus all colours of light at the same point, causing colour fringes.

• Achromatic lens: A lens designed to minimize chromatic aberration by combining two types of glass with different dispersion properties.

• Radio telescope: An instrument that collects and analyses radio waves from space to study celestial objects.

• Atmospheric distortion: Blurring or twinkling of images caused by Earth’s atmosphere bending and scattering light.

• Segmented mirror: A large telescope mirror made of smaller, hexagonal pieces fitted together to act as a single surface.

• Exoplanet: A planet orbiting a star outside our solar system.

• Dark energy: A mysterious force driving the accelerated expansion of the universe, making up most of its energy content.