Instruct: Given a question, retrieve passages that can help answer the question.
Query: What is a telescope?
Telescopes are optical instruments that make distant objects appear magnified by using an arrangement of lenses or curved mirrors and lenses, or various devices used to observe distant objects by their emission, absorption, or reflection of electromagnetic radiation.[1] The first known practical telescopes were refracting telescopes invented in the Netherlands at the beginning of the 17th century, by using glass lenses. They found use in both terrestrial applications and astronomy.
True FOV is the observable world observed though an ocular eyepiece inserted into a telescope. Knowing the true FOV of eyepieces is very useful since it can be used to compare what is seen through the eyepiece to printed or computerized star charts that help identify what is observed. True FOV formula_45 is the division of apparent FOV formula_46 over magnification formula_33.
Newton built his reflecting telescope because he suspected it could prove his theory that white light is composed of a spectrum of colours. Colour distortion (chromatic aberration) was the primary fault of refracting telescopes of Newton's day, and there were many theories as to what caused it. During the mid-1660s with his work on the theory of colour, Newton concluded this defect was caused by the lens of the refracting telescope behaving the same as prisms he was experimenting with, breaking white light into a rainbow of colours around bright astronomical objects. If this were true, then chromatic aberration could be eliminated by building a telescope which did not use a lens – a reflecting telescope.
Based only on uncertain descriptions of the first practical telescope which Hans Lippershey tried to patent in the Netherlands in 1608,[108] Galileo, in the following year, made a telescope with about 3x magnification. He later made improved versions with up to about 30x magnification.[109] With a Galilean telescope, the observer could see magnified, upright images on the earth—it was what is commonly known as a terrestrial telescope or a spyglass. He could also use it to observe the sky; for a time he was one of those who could construct telescopes good enough for that purpose. On 25 August 1609, he demonstrated one of his early telescopes, with a magnification of about 8 or 9, to Venetian lawmakers. His telescopes were also a profitable sideline for Galileo, who sold them to merchants who found them useful both at sea and as items of trade. He published his initial telescopic astronomical observations in March 1610 in a brief treatise entitled Sidereus Nuncius (Starry Messenger).[110]
The telescope has stepper motor drive control with an electrical focusser. The dome is electrically driven and will move automatically as the telescope tracks across the sky. Various cameras can be attached to the telescope to record images and video and display what the telescope sees on a 2 metre wide projector screen in the lecture theatre from where the telescope can be controlled.
"Observable world" describes what can be seen using a telescope, when viewing an object or range the observer may use many different techniques. Understanding what can be viewed and how to view it depends on the field of view. Viewing an object at a size that fits entirely in the field of view is measured using the two telescope properties—focal length and aperture, with the inclusion of an ocular eyepiece with suitable focal length (or diameter). Comparing the observable world and the angular diameter of an object shows how much of the object we see. However, the relationship with the optical system may not result in high surface brightness. Celestial objects are often dim because of their vast distance, and detail may be limited by diffraction or unsuitable optical properties.
Dobson's design allows a builder with minimal skill to make an extremely large telescope out of common items. Dobson optimized the design for observation of faint objects such as star clusters, nebulae, and galaxies (what Amateur Astronomers call "deep sky object"s). These dim objects require a large objective mirror able to gather a large amount of light. Because ""deep sky"" observing often requires travel to dark locations away from city lights, the design benefits from being more compact, portable, and rugged than standard large Newtonian telescopes. John Dobson's telescopes combined several innovations to meet these criteria, including:The design of Dobsonian telescopes has evolved over the years (see ), but most commercial or amateur-built "Dobsonian" telescopes follow many or most of the design concepts and features listed above.
List of optical telescopes List of largest optical reflecting telescopes List of largest optical refracting telescopes List of largest optical telescopes historically List of radio telescopes List of solar telescopes List of space observatories List of telescope parts and construction List of telescope types Category:Telescopes Category:Cosmic-ray telescopes Category:Gamma-ray telescopes Category:Gravitational wave telescopes Category:High energy particle telescopes Category:Infrared telescopes Category:Submillimetre telescopes Category:Ultraviolet telescopes Category:X-ray telescopes
On 18 April 2015, FRB 150418 was detected by the Parkes observatory and within hours, several telescopes including the Australia Telescope Compact Array caught an "afterglow" of the flash, which took six days to fade. The Subaru telescope was used to find what was thought to be the host galaxy and determine its redshift and the implied distance to the burst.
List of largest optical telescopes in the 19th century, are listings of what were, for the time period of the 19th century large optical telescopes. See List of largest optical telescopes in the 20th century for the 1900s. The list includes various refractor and reflector that were active some time between about 1799 to 1901.
Dobsonians are intended to be what is commonly called a "light bucket" operating at low magnification, and therefore the design omits features found in other amateur telescopes such as equatorial tracking. Dobsonians are popular in the amateur telescope making community, where the design was pioneered and continues to evolve. A number of commercial telescope makers also sell telescopes based on this design. The term "Dobsonian" is currently used for a whole range of large-aperture Newtonian reflectors that use some of the basic Dobsonian design characteristics, regardless of the materials from which they are constructed.
In 1927, at Ingalls suggestion, George Ellery Hale recruited Porter to work on the design of what was then to be the largest telescope on earth, the Hale Telescope at Palomar Observatory. Porter moved to Pasadena in December 1928 to work as an associate in optics and instrument design. During the conceptual development of the telescope Porter produced extremely detailed cutaway drawings that were noted for their precision and beauty. Porter's designs were vital to success of the large telescope, which was completed in 1948.
Galileo Galilei turned a telescope to the heavens and recorded what he saw. Since that time, observational astronomy has made steady advances with each improvement in telescope technology.
The Liverpool Telescope (LT) is a fully robotic Ritchey–Chrétien telescope that observes autonomously; i.e., it operates without human intervention. Professional astronomers and other registered users submit observation specifications to be considered by the telescope's robotic control system (RCS) at any time of the day or night using an online GUI. Each night the RCS decides for itself what to observe next based on target visibility and weather conditions.
The 1.2 meter Millimeter-Wave Telescope at the Harvard-Smithsonian Center for Astrophysics and its twin instrument at CTIO in Chile have been studying the distribution and properties of molecular clouds in our galaxy and its nearest neighbours since the 1970s. The telescope is nicknamed "The Mini" because of its unusually small size. At the time it was built, it was the smallest radio telescope in the world. Together, "The Mini" and its twin in Chile have obtained what is by far the most extensive, uniform, and widely used galactic survey of interstellar carbon monoxide. "The Mini" is currently in operation from October to May each year.
The observatory has the largest telescope located in Germany, which is also the largest Schmidt camera in the world. Made by VEB Zeiss Jena (the branch of Carl Zeiss located in Jena in what was then East Germany), this instrument is known as 2m Alfred Jensch Telescope: though its mirror is 2 metres in diameter, the telescope's aperture is 1.34m.
NRO's technology is likely more advanced than its civilian equivalents. In the 1980s the NRO had satellites and software that were capable of determining the exact dimensions of a tank gun. In 2012 the agency donated two space telescopes to NASA. Despite being stored unused, the instruments are superior to the Hubble Space Telescope. One journalist observed, "If telescopes of this caliber are languishing on shelves, imagine what they're actually "using"."
Setting circles are angular measurement scales that can be placed on the two main rotation axes of some telescopes. Since the widespread adoption of digital setting circles, any classical engraved setting circle is now specifically identified as an "analog setting circle" (ASC). By knowing the coordinates of an object (usually given in equatorial coordinates), the telescope user can use the setting circle to align (i.e., point) the telescope in the appropriate direction before looking through its eyepiece. A computerized setting circle is called a "digital setting circle" (DSC). Although digital setting circles can be used to display a telescope's RA and Dec coordinates, they are not simply a digital read-out of what can be seen on the telescope's analog setting circles. As with go-to telescopes, digital setting circle computers (commercial names include Argo Navis, Sky Commander, and NGC Max) contain databases of tens of thousands of celestial objects and projections of planet positions.
One of the collective's main projects is "Radio Astronomy," an art and science project which broadcasts sounds intercepted from space live on the internet and on the airwaves. The project is achieved in collaboration with radio telescopes around the world. The signal from objects observed by these partner telescopes is converted into audio and then broadcast. "Radio Astronomy" has three parts: a sound installation, a live on-air radio transmission, and a live online radio broadcast. Depending on what is being observed by the telescopes, examples of what listeners may hear includes radiation from the Sun, or the planet Jupiter and its interaction with its moons.
Some telescopes cannot achieve the theoretical surface brightness of 100%, while some telescopes can achieve it using a very small-diameter eyepiece. To find what eyepiece is required to get minimum magnification one can rearrange the magnification formula, where it is now the division of the telescope's focal length over the minimum magnification: formula_64. An eyepiece of 35 mm is a non-standard size and would not be purchasable; in this scenario 
to achieve 100% one would require a standard manufactured eyepiece size of 40 mm. As the eyepiece has a larger focal length than the minimum magnification, an abundance of wasted light is not received through the eyes.
List of largest optical telescopes in the 18th century, are listings of what were, for the time period of the 18th century, large optical telescopes. The list includes various refractor and reflector that were active some time between about 1699 to 1801. It is oriented towards astronomy, not terrestrial telescopes (e.g. spyglass).
Dynamic Structures has been involved in the design and construction of most of the world's largest observatories. These include:Currently the company is busy with the design of what will be the largest telescope in the world, called the Thirty Meter Telescope
Hans Lippershey, a German-Dutch spectacle-maker, is commonly credited as being the first to invent the telescope. Lippershey is the first recorded person to apply for a patent for a telescope, however it is unclear if Lippershey was the first to build a telescope. Based only on uncertain descriptions of the telescope which Lippershey tried to obtain a patent for, Galileo made a telescope with about 3x magnification in the following year. Galileo later made improved versions with up to 30x magnification. With a Galilean telescope the observer could see magnified, upright images on the earth—it was what is commonly known as a terrestrial telescope or a spyglass. Galileo could also use it to observe the sky, and for a time was one of those who could construct telescopes good enough for that purpose. On 25 August 1609, Galileo demonstrated one of his early telescopes, with a magnification of up to 8 or 9, to Venetian lawmakers. Galileo's telescopes were also a profitable sideline; selling them to merchants who found them useful both at sea and as items of trade. He published his initial telescopic astronomical observations in March 1610 in a brief treatise entitled "Sidereus Nuncius" ("Starry Messenger").
Taste is the first studio album by The Telescopes, released in 1989 on What Goes On. After What Goes On folded, the album was re-released in 1990 by Cheree, and later released in 2006 by Rev-Ola to include live versions of "There Is No Floor", “ Sadness Pale”, “Threadbare” and “Suicide”.
The late 20th century saw advances in astronomical imaging take place in the form of new hardware, with the construction of giant multi-mirror and segmented mirror telescopes. It would also see the introduction of space based telescopes, such as the Hubble Space Telescope. Operating outside the atmosphere’s turbulence, scattered ambient light and the vagaries of weather allows the Hubble Space Telescope, with a mirror diameter of , to record stars down to the 30th magnitude, some 100 times dimmer than what the 5-meter Mount Palomar Hale telescope could record in 1949.