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Slitless Spectroscopy
Slitless spectroscopy is spectroscopy done without a small slit to allow only light from a small region to be diffracted. It works best in sparsely populated fields, as it spreads each point source out into its spectrum, and crowded fields can be too confused to be useful for some applications. It also faces the problem that for extended sources, nearby emission lines will overlap. This technique is a basic form of snapshot hyperspectral imaging. Slitless spectroscopy is used for astronomical surveys and in fields, such as solar physics, where time evolution is important. Both types of application benefit from higher speed operation of a slitless spectrograph: conventional spectrographs require multiple exposures, scanning the slit across the target, to acquire a complete spectral image, while a slitless spectrograph can capture a complete image plane in one exposure. The Crossley telescope utilized a slitless spectrograph that was originally employed by Nicholas Mayall. The '' ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Spectroscopy
Spectroscopy is the field of study that measures and interprets electromagnetic spectra. In narrower contexts, spectroscopy is the precise study of color as generalized from visible light to all bands of the electromagnetic spectrum. 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 electronic structure of matter to be investigated at the atomic, molecular and macro scale, and over astronomical distances. Historically, spectroscopy originated as the study of the wavelength dependence of the absorption by gas phase matter of visible light dispersed by a prism. Current applications of spectroscopy include biomedical spectroscopy in the areas of tissue analysis and medical imaging. Matter waves and acoustic waves can also be considered forms of radiative energy, and recently gravitational waves have been associa ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Snapshot Hyperspectral Imaging
Snapshot hyperspectral imaging is a method for capturing hyperspectral images during a single integration time of a detector array. No scanning is involved with this method, in contrast to push broom and whisk broom scanning techniques. The lack of moving parts means that motion artifacts should be avoided. This instrument typically features detector arrays with a high number of pixels. Development Although the first known reference to a snapshot hyperspectral imaging device—the Bowen "image slicer"—dates from 1938, the concept was not successful until a larger amount of spatial resolution was available. With the arrival of large-format detector arrays in the late 1980s and early 1990s, a series of new snapshot hyperspectral imaging techniques were developed to take advantage of the new technology: a method which uses a fiber bundle at the image plane and reformatting the fibers in the opposite end of the bundle to a long line, viewing a scene through a 2D grating and re ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Solar Physics
Solar physics is the branch of astrophysics that specializes in the study of the Sun. It intersects with many disciplines of pure physics and astrophysics. Because the Sun is uniquely situated for close-range observing (other stars cannot be resolved with anything like the spatial or temporal resolution that the Sun can), there is a split between the related discipline of observational astrophysics (of distant stars) and observational solar physics. The study of solar physics is also important as it provides a "physical laboratory" for the study of plasma physics. History Ancient times Babylonians were keeping a record of solar eclipses, with the oldest record originating from the ancient city of Ugarit, in modern-day Syria. This record dates to about 1300 BC. Ancient Chinese astronomers were also observing solar phenomena (such as solar eclipses and visible sunspots) with the purpose of keeping track of calendars, which were based on lunar and solar cycles. Unfortunately, rec ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Spectral Imaging
Spectral imaging is imaging that uses multiple bands across the electromagnetic spectrum. While an ordinary camera captures light across three wavelength bands in the visible spectrum, red, green, and blue (RGB), spectral imaging encompasses a wide variety of techniques that go beyond RGB. Spectral imaging may use the infrared, the visible spectrum, the ultraviolet, x-rays, or some combination of the above. It may include the acquisition of image data in visible and non-visible bands simultaneously, illumination from outside the visible range, or the use of optical filters to capture a specific spectral range. It is also possible to capture hundreds of wavelength bands for each pixel in an image. ''Multispectral imaging'' captures a small number of spectral bands, typically three to fifteen, through the use of varying filters and illumination. Many off-the-shelf RGB camera sensors can detect wavelengths of light from 300 nm to 1200 nm. A scene may be illuminated with NIR lig ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Crossley Telescope
The Crossley telescope is a reflecting telescope located at Lick Observatory in the U.S. state of California. It was used between 1895 and 2010, and was donated to the observatory by Edward Crossley, its namesake. It was the largest glass reflecting telescope in the United States for several years after its recommissioning in California. Lick Director, James Edward Keeler, remarked of the Crossley in 1900, "... by far the most effective instrument in the Observatory for certain class of astronomical work." History Given to the Lick Observatory in 1895 by British politician Edward Crossley, it was rebuilt from the ground up as it was on a very flimsy mounting. It was last used in 2010 in the search for extra-solar planets but has been taken out of service due to budget cuts. The mirror, and some of the initial mounts, came from the 36-inch reflector originally mounted in Andrew Ainslie Common's backyard Ealing observatory. He had used it from 1879 to 1886 to prove the conce ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nicholas Mayall
Nicholas Ulrich Mayall (May 9, 1906 – January 5, 1993) was an American observational astronomer. After obtaining his doctorate from the University of California, Berkeley, Mayall worked at the Lick Observatory, where he remained from 1934 to 1960, except for a brief period at MIT's Radiation Laboratory during World War II. During his time at Lick, Mayall contributed to astronomical knowledge of nebulae, supernovae, spiral galaxy internal motions, the redshifts of galaxies, and the origin, age, and size of the Universe. He played a significant role in the planning and construction of Lick's reflector, which represented a major improvement over its earlier telescope. From 1960, Mayall spent 11 years as director of the Kitt Peak National Observatory until his retirement in 1971. Under his leadership KPNO, and the Cerro Tololo Inter-American Observatory, developed into two of the world's top research observatories, equipped with premier telescopes. Mayall was responsible ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Henry Draper Catalogue
The ''Henry Draper Catalogue'' (HD) is an astronomical star catalogue published between 1918 and 1924, giving spectroscopic classifications for 225,300 stars; it was later expanded by the ''Henry Draper Extension'' (HDE), published between 1925 and 1936, which gave classifications for 46,850 more stars, and by the ''Henry Draper Extension Charts'' (HDEC), published from 1937 to 1949 in the form of charts, which gave classifications for 86,933 more stars. In all, 359,083 stars were classified as of August 2017. The HD catalogue is named after Henry Draper, an amateur astronomer, and covers the entire sky almost completely down to an apparent photographic magnitude of about 9; the extensions added fainter stars in certain areas of the sky. The construction of the ''Henry Draper Catalogue'' was part of a pioneering effort to classify stellar spectra, and its catalogue numbers are commonly used as a way of identifying stars. History The origin of the ''Henry Draper Catalogue'' d ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Harvard College Observatory
The Harvard College Observatory (HCO) is an institution managing a complex of buildings and multiple instruments used for astronomical research by the Harvard University Department of Astronomy. It is located in Cambridge, Massachusetts, United States, and was founded in 1839. With the Smithsonian Astrophysical Observatory, it forms part of the Center for Astrophysics Harvard & Smithsonian. HCO houses the Harvard Plate Stacks, a collection of approximately 600,000 astronomical plates taken between the mid-1880s and 1989 (with a gap from 1953–1968). This 100-year coverage is a unique resource for studying temporal variations in the universe. The Digital Access to a Sky Century @ Harvard project scanned and 429,274 direct image plates, leaving nearly 200,000 spectra and other photographic plates yet to be digitized. In 2024, a new database, StarGlass, was created to combine the scientific data from the plates with the Plate Stack's archival holdings. History In 1839, the Ha ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Williamina Fleming
Williamina Paton Stevens Fleming (15 May 1857 – 21 May 1911) was a pioneering Scottish astronomer, who made significant contributions to the field despite facing gender biases. She was a single mother hired by the director of the Harvard College Observatory to help in the photographic classification of stellar spectra. She helped develop a common designation system for stars and cataloged more than ten thousand stars, 59 gaseous nebulae, over 310 variable stars, and 10 novae and other astronomical phenomena. Among several career achievements that advanced astronomy, Fleming is noted for her discovery of the Horsehead Nebula in 1888. Fleming's work has had a lasting impact on our understanding of the universe. Early life Williamina Paton Stevens was born in Dundee, Scotland, at 86 Nethergate, on 15 May 1857 to Mary Walker and Robert Stevens, a carver and gilder. She was one of six children. Her younger sister, Johanna Stevens, would also later work at Harvard College O ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Annie Jump Cannon
Annie Jump Cannon (; December 11, 1863 – April 13, 1941) was an American astronomer whose cataloging work was instrumental in the development of contemporary stellar classification. With Edward C. Pickering, she is credited with the creation of the Stellar classification, Harvard Classification Scheme, which was the first serious attempt to organize and classify stars based on their temperatures and spectral types. She was nearly deaf throughout her career after 1893, as a result of scarlet fever. She was a Suffragette, suffragist and a member of the National Woman's Party, National Women's Party. Personal life Cannon was born on December 11, 1863, in Dover, Delaware. She was the eldest of three daughters born to Wilson Cannon, a Delaware shipbuilder and state senator, and his second wife, Mary Jump. Cannon's mother was the first person to teach her the constellations and she encouraged her to follow her own interests, suggesting that she pursue studies in mathematics, chemistry ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Florence Cushman
Florence Cushman (1860–1940) was an American astronomer specializing in stellar classification at the Harvard College Observatory who worked on the ''Henry Draper Catalogue''. Life Florence was born in Boston, Massachusetts, and received her early education at Charlestown High School, where she graduated in 1877. In 1888, she began work at the Harvard College Observatory as an employee of Edward Pickering, observing and classifying stars. Florence was one of the "Harvard Computers" who worked under Pickering and, following his death in 1919, Annie Jump Cannon. Her classifications of stellar spectra contributed to ''Henry Draper Catalogue'' between 1918 and 1934. She stayed as an astronomer at the Observatory until 1937 and died January 30, 1940, at the age of 80. Career at the Harvard College Observatory Florence Cushman worked and was a member of the Harvard College Observatory from 1888 to 1937. She started her work by observing and classifying starts as one of Anni ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Specular Reflection
Specular reflection, or regular reflection, is the mirror-like reflection (physics), reflection of waves, such as light, from a surface. The law of reflection states that a reflected ray (optics), ray of light emerges from the reflecting surface at the same angle to the surface normal as the incident ray, but on the opposing side of the surface normal in the plane formed by the incident and reflected rays. The earliest known description of this behavior was recorded by Hero of Alexandria (Anno Domini, AD c. 10–70). Later, Ibn al-Haytham, Alhazen gave a complete statement of the law of reflection. He was first to state that the incident ray, the reflected ray, and the normal to the surface all lie in a same plane perpendicular to reflecting plane. Specular reflection may be contrasted with diffuse reflection, in which light is scattered away from the surface in a range of directions. Law of reflection When light encounters a boundary of a material, it is affected by the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
