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Small Telescope
A small telescope is generally considered by professional astronomers to be any reflecting telescope with a primary mirror that is less than in diameter. By amateur standards, a small telescope can have a primary mirror/aperture less than in diameter. Little if any professional-level research is performed with refracting telescopes in the modern era of astronomy. Small telescopes dominate astronomical research in the fields of asteroid/comet discovery/observation, variable star photometry, supernova/nova discovery, and colorimetry/polarimetry of the Solar System's planets. Because of their limited light-gathering capability, small telescopes are usually not well-suited to spectroscopy, although some useful spectroscopic work can be performed with reflecting telescopes with a primary mirror as small as when equipped with the increasingly sophisticated CCD imaging and spectroscopic instrumentation that has become available to amateur astronomers in the 21st century. Most teles ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Astronomer
An astronomer is a scientist in the field of astronomy who focuses their studies on a specific question or field outside the scope of Earth. They observe astronomical objects such as stars, planets, natural satellite, moons, comets and galaxy, galaxies – in either observational astronomy, observational (by analyzing the data) or theoretical astronomy. Examples of topics or fields astronomers study include planetary science, Sun, solar astronomy, the Star formation, origin or stellar evolution, evolution of stars, or the galaxy formation and evolution, formation of galaxies. A related but distinct subject is physical cosmology, which studies the Universe as a whole. Types Astronomers usually fall under either of two main types: observational astronomy, observational and theoretical astronomy, theoretical. Observational astronomers make direct observations of Astronomical object, celestial objects and analyze the data. In contrast, theoretical astronomers create and investigate C ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Polarimetry
Polarimetry is the measurement and interpretation of the polarization of transverse waves, most notably electromagnetic waves, such as radio or light waves. Typically polarimetry is done on electromagnetic waves that have traveled through or have been reflected, refracted or diffracted by some material in order to characterize that object. Plane polarized light: According to the wave theory of light, an ordinary ray of light is considered to be vibrating in all planes of right angles to the direction of its propagation. If this ordinary ray of light is passed through a nicol prism, the emergent ray has its vibration only in one plane. Applications Polarimetry of thin films and surfaces is commonly known as ellipsometry. Polarimetry is used in remote sensing applications, such as planetary science, astronomy, and weather radar. Polarimetry can also be included in computational analysis of waves. For example, radars often consider wave polarization in post-processing to imp ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ritchey–Chrétien Telescope
A Ritchey–Chrétien telescope (RCT or simply RC) is a specialized variant of the Cassegrain telescope that has a hyperbolic primary mirror and a hyperbolic secondary mirror designed to eliminate off-axis optical errors (coma). The RCT has a wider field of view free of optical errors compared to a more traditional reflecting telescope configuration. Since the mid 20th century, a majority of large professional research telescopes have been Ritchey–Chrétien configurations; some well-known examples are the Hubble Space Telescope, the Keck telescopes and the ESO Very Large Telescope. History The Ritchey–Chrétien telescope was invented in the early 1910s by American astronomer George Willis Ritchey and French astronomer Henri Chrétien. Ritchey constructed the first successful RCT, which had an aperture diameter of in 1927 (e.g. Ritchey 24-inch reflector). The second RCT was a instrument constructed by Ritchey for the United States Naval Observatory; that telescope is st ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Maksutov-Newtonian
The Maksutov (also called a "Mak") is a catadioptric telescope design that combines a spherical mirror with a weakly negative meniscus lens in a design that takes advantage of all the surfaces being nearly "spherically symmetrical". The negative lens is usually full diameter and placed at the entrance pupil of the telescope (commonly called a "corrector plate" or "meniscus corrector shell"). The design corrects the problems of off-axis aberrations such as coma found in reflecting telescopes while also correcting chromatic aberration. It was patented in 1941 by Russian optician Dmitri Dmitrievich Maksutov. Maksutov based his design on the idea behind the Schmidt camera of using the spherical errors of a negative lens to correct the opposite errors in a spherical primary mirror. The design is most commonly seen in a Cassegrain variation, with an integrated secondary, that can use all-spherical elements, thereby simplifying fabrication. Maksutov telescopes have been sold on the ama ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Maksutov-Cassegrain
The Maksutov (also called a "Mak") is a catadioptric telescope design that combines a spherical mirror with a weakly negative meniscus lens in a design that takes advantage of all the surfaces being nearly "spherically symmetrical". The negative lens is usually full diameter and placed at the entrance pupil of the telescope (commonly called a "corrector plate" or "meniscus corrector shell"). The design corrects the problems of off-axis aberrations such as coma found in reflecting telescopes while also correcting chromatic aberration. It was patented in 1941 by Russian optician Dmitri Dmitrievich Maksutov. Maksutov based his design on the idea behind the Schmidt camera of using the spherical errors of a negative lens to correct the opposite errors in a spherical primary mirror. The design is most commonly seen in a Cassegrain variation, with an integrated secondary, that can use all-spherical elements, thereby simplifying fabrication. Maksutov telescopes have been sold on the ama ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Schmidt–Cassegrain Telescope
The Schmidt–Cassegrain is a catadioptric telescope that combines a Cassegrain reflector's optical path with a Schmidt corrector plate to make a compact astronomical instrument that uses simple spherical surfaces. Invention and design The American astronomer and lens designer James Gilbert Baker first proposed a Cassegrain design for Bernhard Schmidt's Schmidt camera in 1940. The optical shop at Mount Wilson Observatory manufactured the first one during World War II as part of their research into optical designs for the military. As in the Schmidt camera, this design uses a spherical primary mirror and a Schmidt corrector plate to correct for spherical aberration. In this Cassegrain configuration the convex secondary mirror acts as a field flattener and relays the image through the perforated primary mirror to a final focal plane located behind the primary. Some designs include additional optical elements (such as field flatteners) near the focal plane. The first large tele ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Newtonian Telescope
The Newtonian telescope, also called the Newtonian reflector or just a Newtonian, is a type of reflecting telescope invented by the English scientist Sir Isaac Newton, using a concave primary mirror and a flat diagonal secondary mirror. Newton's first reflecting telescope was completed in 1668 and is the earliest known functional reflecting telescope. The Newtonian telescope's simple design has made it very popular with amateur telescope makers. Description 
A Newtonian telescope is composed of a primary mirror or objective, usually parabolic in shape, and a smaller mirror called the "secondary" which is flat. ...
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Apochromatic
An apochromat, or apochromatic lens (apo), is a photographic or other lens that has better correction of chromatic and spherical aberration than the much more common achromat lenses. Explanation Chromatic aberration is the phenomenon of different colors focusing at different distances from a lens. In photography, chromatic aberration produces soft overall images, and color fringing at high-contrast edges, like an edge between black and white. Astronomers face similar problems, particularly with telescopes that use lenses rather than mirrors. ''Achromatic'' lenses are corrected to bring ''two'' wavelengths into focus in the same plane – typically red (~0.590 µm) and blue (~0.495 µm). ''Apo''chromatic lenses are designed to bring ''three'' colors into focus in the same plane – typically red (~0.620 µm), green (~0.530 µm), and blue (~0.465 µm). The residual color error (secondary spectrum) can be up to an order of magnitude less than for an achro ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Achromatic Lens
An achromatic lens or achromat is a lens that is designed to limit the effects of chromatic and spherical aberration. Achromatic lenses are corrected to bring two wavelengths (typically red and blue) into focus on the same plane. The most common type of achromat is the achromatic doublet, which is composed of two individual lenses made from glasses with different amounts of dispersion. Typically, one element is a negative (concave) element made out of flint glass such as F2, which has relatively high dispersion, and the other is a positive (convex) element made of crown glass such as BK7, which has lower dispersion. The lens elements are mounted next to each other, often cemented together, and shaped so that the chromatic aberration of one is counterbalanced by that of the other. In the most common type (shown), the positive power of the crown lens element is not quite equalled by the negative power of the flint lens element. Together they form a weak positive lens that will b ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Astrophotography
Astrophotography, also known as astronomical imaging, is the photography or imaging of astronomical objects, celestial events, or areas of the night sky. The first photograph of an astronomical object (the Moon) was taken in 1840, but it was not until the late 19th century that advances in technology allowed for detailed stellar photography. Besides being able to record the details of extended objects such as the Moon, Sun, and planets, modern astrophotography has the ability to image objects invisible to the human eye such as dim stars, nebulae, and galaxies. This is done by long time exposure since both film and digital cameras can accumulate and sum photons over these long periods of time. Photography using extended exposure-times revolutionized the field of professional astronomical research, recording hundreds of thousands of new stars, and nebulae invisible to the human eye. Specialized and ever-larger optical telescopes were constructed as essentially big cameras to rec ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Charge-coupled Device
A charge-coupled device (CCD) is an integrated circuit containing an array of linked, or coupled, capacitors. Under the control of an external circuit, each capacitor can transfer its electric charge to a neighboring capacitor. CCD sensors are a major technology used in digital imaging. In a CCD image sensor, pixels are represented by p-doped metal–oxide–semiconductor (MOS) capacitors. These MOS capacitors, the basic building blocks of a CCD, are biased above the threshold for inversion when image acquisition begins, allowing the conversion of incoming photons into electron charges at the semiconductor-oxide interface; the CCD is then used to read out these charges. Although CCDs are not the only technology to allow for light detection, CCD image sensors are widely used in professional, medical, and scientific applications where high-quality image data are required. In applications with less exacting quality demands, such as consumer and professional digital cameras, act ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Spectroscopy
Spectroscopy is the field of study that measures and interprets the electromagnetic spectra that result from the interaction between electromagnetic radiation and matter as a function of the wavelength or frequency of the radiation. Matter waves and acoustic waves can also be considered forms of radiative energy, and recently gravitational waves have been associated with a spectral signature in the context of the Laser Interferometer Gravitational-Wave Observatory (LIGO) In simpler terms, spectroscopy is the precise study of color as generalized from visible light to all bands of the electromagnetic spectrum. Historically, spectroscopy originated as the study of the wavelength dependence of the absorption by gas phase matter of visible light dispersed by a prism. Spectroscopy, primarily in the electromagnetic spectrum, is a fundamental exploratory tool in the fields of astronomy, chemistry, materials science, and physics, allowing the composition, physical structure and e ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
