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Hadley Octant
The octant, also called a reflecting quadrant, is a reflecting instrument used in navigation. Etymology The name ''octant'' derives from the Latin ''octans'' meaning ''eighth part of a circle'', because the instrument's arc is one eighth of a circle. ''Reflecting quadrant'' derives from the instrument using mirrors to reflect the path of light to the observer and, in doing so, doubles the angle measured. This allows the instrument to use a one-eighth of a turn to measure a quarter-turn or quadrant. Origin of the octant Newton's reflecting quadrant Isaac Newton's reflecting quadrant was invented around 1699. A detailed description of the instrument was given to Edmond Halley, but the description was not published until after Halley's death in 1742. It is not known why Halley did not publish the information during his life, as this prevented Newton from getting the credit for the invention that is generally given to John Hadley and Thomas Godfrey. One copy of this inst ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sextant
A sextant is a doubly reflecting navigation instrument that measures the angular distance between two visible objects. The primary use of a sextant is to measure the angle between an astronomical object and the horizon for the purposes of celestial navigation. The estimation of this angle, the altitude, is known as ''sighting'' or ''shooting'' the object, or ''taking a sight''. The angle, and the time when it was measured, can be used to calculate a position line on a nautical or aeronautical chart—for example, sighting the Sun at noon or Polaris at night (in the Northern Hemisphere) to estimate latitude (with sight reduction). Sighting the height of a landmark can give a measure of ''distance off'' and, held horizontally, a sextant can measure angles between objects for a position on a chart. A sextant can also be used to measure the lunar distance between the moon and another celestial object (such as a star or planet) in order to determine Greenwich Mean Time and hence ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chromatic Aberration
In optics, chromatic aberration (CA), also called chromatic distortion and spherochromatism, is a failure of a lens to focus all colors to the same point. It is caused by dispersion: the refractive index of the lens elements varies with the wavelength of light. The refractive index of most transparent materials decreases with increasing wavelength. Since the focal length of a lens depends on the refractive index, this variation in refractive index affects focusing. Chromatic aberration manifests itself as "fringes" of color along boundaries that separate dark and bright parts of the image. Types There are two types of chromatic aberration: ''axial'' (''longitudinal''), and ''transverse'' (''lateral''). Axial aberration occurs when different wavelengths of light are focused at different distances from the lens (focus ''shift''). Longitudinal aberration is typical at long focal lengths. Transverse aberration occurs when different wavelengths are focused at different positions i ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Speculum Metal
Speculum metal is a mixture of around two-thirds copper and one-third tin, making a white brittle alloy that can be polished to make a highly reflective surface. It was used historically to make different kinds of mirrors from personal grooming aids to optical devices until it was replaced by more modern materials such as metal-coated glass mirrors. Speculum metal mixtures usually contain two parts copper to one part tin along with a small amount of arsenic, although there are other mixtures containing silver, lead, or zinc. This is about twice the proportion of tin to copper typically used in bronze alloys. Archaeologists and others prefer to call it "high-tin bronze", although this broad term is also used for other alloys such as bell metal, which is typically around 20% tin. Large speculum metal mirrors are hard to manufacture, and the alloy is prone to tarnish, requiring frequent re-polishing. However, it was the only practical choice for large mirrors in high-precision opt ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Prism (optics)
An optical prism is a transparent optics, optical element with flat, polished surfaces that are designed to refraction, refract light. At least one surface must be angled — elements with two parallel surfaces are ''not'' prisms. The most familiar type of optical prism is the triangular prism, which has a triangular base and rectangular sides. Not all optical prisms are prism (geometry), geometric prisms, and not all geometric prisms would count as an optical prism. Prisms can be made from any material that is transparent to the wavelengths for which they are designed. Typical materials include glass, acrylic glass, acrylic and fluorite#Optics, fluorite. A dispersive prism can be used to break white#White light, white light up into its constituent spectral colors (the colors of the rainbow) as described in the following section. Other types of prisms noted below can be used to reflection (physics), reflect light, or to split light into components with different polarization (w ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Caleb Smith (astronomer)
Caleb Smith may refer to: * Caleb Blood Smith (1808–1864), American journalist and politician * Caleb Smith (skeleton racer) (born 1983), American skeleton racer * Caleb Smith (baseball) (born 1991), American baseball pitcher * Caleb Smith (soccer) Caleb Smith (born October 15, 1996) is an American professional soccer player who most recently played as a defender for USL Championship club Pittsburgh Riverhounds SC. Youth career At the age of five, Smith began playing soccer recreational ... (born 1996), American soccer player * Caleb L. Smith (1829–1890), American builder and politician from New York {{hndis, Smith, Caleb ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Astroscope (instrument)
''Transformers: Armada'', known in Japan as , is an anime series which debuted on August 23, 2002. As the first series co-produced between the American toy company Hasbro and their Japanese counterpart Takara, ''Armada'' begins a new continuity/universe for ''Transformers'', with no ties to any of the previous series, including the immediately prior '' Transformers: Robots in Disguise'' in 2001. It inspired two sequels, '' Transformers: Energon'' and '' Transformers: Cybertron''. Hasbro handled the distribution of the English license, while Takara handled the distribution of the Japanese license. ''Transformers: Armada'' and both of its following series are all part of a saga known as the "Unicron Trilogy". Plot On the planet of Cybertron, war rages between the two factions known as the Autobots and the Decepticons over the race of smaller, power-enhancing Transformers called Mini-Cons. Seeking to flee the conflict that surrounds them, the Mini-Cons escape Cybertron with the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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