This was known as the revolutionary stargazing tool that changed Earth's standing in the Universe. Although Galileo didn't invent the telescope he was the first to use it, and from using it made some notes and drawings of what he saw.
Galileo's drawings of the moon saw through his telescope, these are very basic but considering this is back in the 1600's its still quite impressive.
Here are another two drawings by Galileo, this time of jupiter and its moons, again very basic and not really too impressive, but over the next 400 years technology in telescopes has taken a big leap.
Telescopes work one of Three ways,
Refracting Telescopes use a large objective lens as their primary light-collecting element. Meade refractors, in all models and apertures, include achromatic (2-element) objective lenses, in order to reduce or virtually eliminate the false color (chromatic aberration) that results in the telescopic image when light passes through a lens.
Reflecting Telescopes use a concave primary mirror to collect light and form an image. In the Newtonian type of reflector, light is reflected by a small, flat secondary mirror to the side of the main tube for observation of the image.
Mirror-Lens (Catadioptric) Telescopes employ both mirrors and lenses, resulting in optical configurations that achieve remarkable image quality and resolution, while housing the optics in extremely short, highly portable optical tubes.
The best Telescope we have to date would have the be the 'Hubble Space Telescope'.
In 1990, the Hubble Space Telescope, named in honour of astronomer Edwin Hubble, was launched into orbit around the Earth.
The telescope, a basic Reflector with a 94.5 inch (2.4 meter) mirror, was packed with instruments that would give the astronomers clear views of the universe in visible, infrared and ultraviolet light. Without Earth's atmosphere blocking its view, Hubble would be able to observe detail of astronomical objects that had never been seen before.
Here is a simple diagram that explains how the telescope works.
Hubble is a type of telescope known as a Cassegrain reflector. Light hits the telescope's main mirror, or primary mirror. It bounces off the primary mirror and encounters a secondary mirror. The secondary mirror focuses the light through a hole in the center of the primary mirror that leads to the telescope's science instruments.
Every 97 minutes, Hubble completes a spin around Earth, moving at the speed of about five miles per second (8 km per second) — fast enough to travel across the United States in about 10 minutes. As it travels, Hubble's mirror captures light and directs it into its several science instruments.
People often mistakenly believe that a telescope's power lies in its ability to magnify objects. Telescopes actually work by collecting more light than the human eye can capture on its own. The larger a telescope's mirror, the more light it can collect, and the better its vision. Hubble's primary mirror is 94.5 inches (2.4 m) in diameter. This mirror is small compared with those of current ground-based telescopes, which can be 400 inches (1,000 cm) and up, but Hubble's location beyond the atmosphere gives it remarkable clarity.
The Wide Field Camera 3 (WFC3) sees three different kinds of light: near-ultraviolet, visible and near-infrared, though not simultaneously. Its resolution and field of view are much greater than that of Hubble's other instruments. WFC3 is one of Hubble's two newest instruments, and will be used to study dark energy and dark matter, the formation of individual stars and the discovery of extremely remote galaxies previously beyond Hubble's vision.
The Cosmic Origins Spectrograph (COS), Hubble's other new instrument, is a spectrograph that sees exclusively in ultraviolet light. Spectrographs acts something like prisms, separating light from the cosmos into its component colors. This provides a wavelength "fingerprint" of the object being observed, which tells us about its temperature, chemical composition, density, and motion. COS will improve Hubble's ultraviolet sensitivity at least 10 times, and up to 70 times when observing extremely faint objects.
The Advanced Camera for Surveys (ACS) sees visible light, and is designed to study some of the earliest activity in the universe. ACS helps map the distribution of dark matter, detects the most distant objects in the universe, searches for massive planets, and studies the evolution of clusters of galaxies. ACS partially stopped working in 2007 due to an electrical short, but was repaired during Servicing Mission 4 in May 2009.
The Space Telescope Imaging Spectrograph (STIS) is a spectrograph that sees ultraviolet, visible and near-infrared light, and is known for its ability to hunt black holes. While COS works best with small sources of light, such as stars or quasars, STIS can map out larger objects like galaxies. STIS stopped working due to a technical failure on August 3, 2004, but was also repaired during Servicing Mission 4.
The Near Infrared Camera and Multi-Object Spectrometer (NICMOS) is Hubble's heat sensor. Its sensitivity to infrared light — perceived by humans as heat — lets it observe objects hidden by interstellar dust, like stellar birth sites, and gaze into deepest space.
Finally, the Fine Guidance Sensors (FGS) are devices that lock onto "guide stars" and keep Hubble pointed in the right direction. They can be used to precisely measure the distance between stars, and their relative motions.
Here are some images from the Hubble Space Telescopes:
The Crab Nebula,
The Crab Nebula is a supernova remnant, all that remains of a tremendous stellar explosion. Observers in China and Japan recorded the supernova nearly 1,000 years ago, in 1054.
Colliding Galaxies,
These two spiral galaxies, drawn together by gravity, started to interact a few hundred million years ago. The Antennae Galaxies are the nearest and youngest examples of a pair of colliding galaxies.
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