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Astronomical Telescope

    A telescope is an instrument that aids in the observation of remote objects by collecting electromagnetic radiation (such as visible light). The first known practical telescopes were invented in the Netherlands at the beginning of the 17th century, using glass lenses. They found use in terrestrial applications and astronomy.     Within a few decades, the reflecting telescope was invented, which used mirrors. In the 20th century many new types of telescopes were invented, including radio telescopes in the 1930s and infrared telescopes in the 1960s. The word telescope now refers to a wide range of instruments detecting different regions of the electromagnetic spectrum, and in some cases other types of detectors.     The word "telescope" (from the Ancient Greek τῆλε, tele "far" and σκοπεῖν, skopein "to look or see"; τηλεσκόπος, teleskopos "far-seeing") was coined in 1611 by the Greek mathematician Giovanni Demisiani for one of Galileo Galilei's inst..
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Posted: 16/03/2016

Refracting Astronomical Telescope

    A refracting or refractor telescope is a type of optical telescope that uses a lens as its objective to form an image (also referred to a dioptric telescope). The refracting telescope design was originally used in spy glasses and astronomical telescopes but is also used for long focus camera lenses. Although large refracting telescopes were very popular in the second half of the 19th century, for most research purposes the refracting telescope has been superseded by the reflecting telescope which allows larger apertures. A refractor's magnification is calculated by dividing the focal length of the objective lens by that of the eyepiece. Image of a refracting telescope from the Cincinnati Observatory in 1848     1.0 Invention     Refractors were the earliest type of optical telescope. The first practical refracting telescopes appeared in the Netherlands about 1608, and were credited to three individuals, Hans Lippershey and Zacha..
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Posted: 20/03/2016

Reflecting Astronomical Telescope

    A reflecting telescope (also called a reflector) is an optical telescope which uses a single or combination of curved mirrors that reflect light and form an image. The reflecting telescope was invented in the 17th century as an alternative to the refracting telescope which, at that time, was a design that suffered from severe chromatic aberration. Although reflecting telescopes produce other types of optical aberrations, it is a design that allows for very large diameter objectives. Almost all of the major telescopes used in astronomy research are reflectors. Reflecting telescopes come in many design variations and may employ extra optical elements to improve image quality or place the image in a mechanically advantageous position. Since reflecting telescopes use mirrors, the design is sometimes referred to as a "catoptric" telescope. 24 inch convertible Newtonian/Cassegrain reflecting telescope on display at the Franklin Institute     1.0 H..
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Posted: 20/03/2016

Laser Rangefinder

    A laser rangefinder is a rangefinder which uses a laser beam to determine the distance to an object. The most common form of laser rangefinder operates on the time of flight principle by sending a laser pulse in a narrow beam towards the object and measuring the time taken by the pulse to be reflected off the target and returned to the sender. Due to the high speed of light, this technique is not appropriate for high precision sub-millimeter measurements, where triangulation and other techniques are often used. A long range laser rangefinder is capable of measuring distance up to 20 km; mounted on a tripod with an angular mount. The resulting system also provides azimuth and elevation measurements.     1.0 Pulse     The pulse may be coded to reduce the chance that the rangefinder can be jammed. It is possible to use Doppler effect techniques to judge whether the object is moving towards or away from the rangefinder, and if so, how fa..
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Posted: 20/03/2016

Microscope

    A microscope (from the Ancient Greek: μικρός, mikrós, "small" and σκοπεῖν, skopeîn, "to look" or "see") is an instrument used to see objects that are too small for the naked eye. The science of investigating small objects using such an instrument is called microscopy. Microscopic means invisible to the eye unless aided by a microscope.     There are many types of microscopes. The most common (and the first to be invented) is the optical microscope, which uses light to image the sample. Other major types of microscopes are the electron microscope (both the transmission electron microscope and the scanning electron microscope), the ultramicroscope, and the various types of scanning probe microscope.     On October 8, 2014, the Nobel Prize in Chemistry was awarded to Eric Betzig, William Moerner and Stefan Hell for "the development of super-resolved fluorescence microscopy," which brings "optical microscopy into the nanodimension". Uses: Smal..
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Posted: 20/03/2016

Optical Microscope

    The optical microscope, often referred to as light microscope, is a type of microscope which uses visible light and a system of lenses to magnify images of small samples. Optical microscopes are the oldest design of microscope and were possibly invented in their present compound form in the 17th century. Basic optical microscopes can be very simple, although there are many complex designs which aim to improve resolution and sample contrast.     The image from an optical microscope can be captured by normal light-sensitive cameras to generate a micrograph. Originally images were captured by photographic film but modern developments in CMOS and charge-coupled device (CCD) cameras allow the capture of digital images. Purely digital microscopes are now available which use a CCD camera to examine a sample, showing the resulting image directly on a computer screen without the need for eyepieces.     Alternatives to optical microscopy which do not use v..
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Posted: 20/03/2016

Binoculars

    Binoculars, field glasses or binocular telescopes are a pair of identical or mirror-symmetrical telescopes mounted side-by-side and aligned to point accurately in the same direction, allowing the viewer to use both eyes (binocular vision) when viewing distant objects. Most are sized to be held using both hands, although sizes vary widely from opera glasses to large pedestal mounted military models.     Unlike a (monocular) telescope, binoculars give users a three-dimensional image: for nearer objects the two views, presented to each of the viewer's eyes from slightly different viewpoints, produce a merged view with an impression of depth. A typical Porro prism binoculars design   Binoculars, by Father Chérubin d'Orléans, 1681, Musée des Arts et Métiers     1.0 Optical designs 1.1 Galilean binoculars     Almost from the invention of the telescope in the 17th century the advantages of mounting t..
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Posted: 20/03/2016

Porro Prism Binoculars

    In optics, a Porro prism, named for its inventor Ignazio Porro, is a type of reflection prism used in optical instruments to alter the orientation of an image.     It consists of a block of glass shaped as a right geometric prism with right-angled triangular end faces. In operation, light enters the large rectangular face of the prism, undergoes total internal reflection twice from the sloped faces, and exits again through the large rectangular face. Because the light exits and enters the glass only at normal incidence, the prism is not dispersive.     An image travelling through a Porro prism is rotated by 180° and exits in the opposite direction offset from its entrance point. Since the image is reflected twice, the handedness of the image is unchanged.     Porro prisms are most often used in pairs, forming a double Porro prism. A second prism, rotated 90° with respect to the first, is placed such that the beam will traverse both p..
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Posted: 21/03/2016

Roof Prism Binoculars

    A roof prism (also called a Dach prism or Dachkanten prism, from the German: "Dachkante", lit. roof edge) is a reflective optical prism containing a section where two faces meet at a 90° angle. These two 90° faces resemble the roof of a building, giving this prism type its name. Reflection from the two 90° faces returns an image that is flipped laterally across the axis where the faces meet.     Characteristic for a roof prism is that the beam is split in half, with one half of the beam hitting first one face then the other face, while it is invert for the other half of the beam. Therefore a roof prism can be used only with some distance to focal planes, or the "edge" of the roof would introduce slight distortions. Furthermore the angle between the two faces has to be very close to 90°, or image quality would be degraded.     The simplest roof prism is the Amici roof prism, with other common roof prism designs being the Abbe–Koenig prism, the Sch..
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Posted: 21/03/2016

Zoom Lens

    A zoom lens is a mechanical assembly of lens elements for which the focal length (and thus angle of view) can be varied, as opposed to a fixed focal length (FFL) lens (see prime lens).     A true zoom lens, also called a parfocal lens, is one that maintains focus when its focal length changes. A lens that loses focus during zooming is more properly called a varifocal lens. Despite being marketed as zoom lenses, virtually all consumer lenses with variable focal lengths use varifocal design.     Zoom lenses afford the user the convenience of variable focal length, at the cost of complexity. Zoom lenses achieve this convenience through compromises on image quality, weight, dimensions, aperture, autofocus performance (both speed and accuracy), build quality, and cost of manufacture. For example, all zoom lenses suffer from at least slight, if not considerable, loss of image resolution at their maximum aperture, especially at the extremes of their foc..
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Posted: 21/03/2016

Monocular

    A monocular is a modified refracting telescope used to magnify the images of distant objects by passing light through a series of lenses and usually prisms, the application of prisms resulting in a lightweight, compact telescope. Volume and weight are less than half those of binoculars of similar optical properties, making it easy to carry, and also proportionally less expensive. Monoculars produce 2-dimensional images, while binoculars add perception of depth (3 dimensions), assuming one has binocular vision.     Monoculars are ideally suited to those with vision in only one eye, or where compactness and low weight are important (e.g. hiking). However, monoculars are sometimes preferred by those with normal vision, where using both eyes through binoculars causes difficulties.     A monocular with a straight optical path is relatively long; prisms are normally used to fold the optical path to make an instrument which is much shorter (see the entr..
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Posted: 21/03/2016

Night Vision

    Night vision is the ability to see in low light conditions. Whether by biological or technological means, night vision is made possible by a combination of two approaches: sufficient spectral range, and sufficient intensity range. Humans have poor night vision compared to many animals, in part because the human eye lacks a tapetum lucidum. Two American soldiers pictured during the 2003 Iraq War seen through an image intensifier     1.0 Types of ranges 1.1 Spectral range     Night-useful spectral range techniques can sense radiation that is invisible to a human observer. Human vision is confined to a small portion of the electromagnetic spectrum called visible light. Enhanced spectral range allows the viewer to take advantage of non-visible sources of electromagnetic radiation (such as near-infrared or ultraviolet radiation). Some animals such as the mantis shrimp can see using much more of the infrared and/or ultraviolet..
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Posted: 22/03/2016

Spotting Scope

    A spotting scope is a small portable telescope with added optics to present an erect image, optimized for the observation of terrestrial objects. They are used for birdwatching and other naturalist activities, for hunting, verifying a marksman's shots, surveillance, and for any other application that requires more magnification than a pair of binoculars, typically on the order of 20× to 60×.     The light-gathering power and resolution of a spotting scope is determined by the diameter of the objective lens, typically between 50 and 80 mm (2.0 and 3.1 in). The larger the objective, the more massive and expensive the telescope.     The optical assembly has a small refracting objective lens, an image erecting system that uses either image erecting relay lenses or prisms (Porro prisms or roof prisms), and an eyepiece that is usually removable and interchangeable to give different magnifications. Other telescope designs are used such as Schmidt and Ma..
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Posted: 22/03/2016

Laser Diode

    A laser diode, or LD, is an electrically pumped semiconductor laser in which the active laser medium is formed by a p-n junction of a semiconductor diode similar to that found in a light-emitting diode.     The laser diode is the most common type of laser produced with a wide range of uses that include fiber optic communications, barcode readers, laser pointers, CD/DVD/Blu-ray Disc reading and recording, laser printing, laser scanning and increasingly directional lighting sources. a packaged laser diode shown with a penny for scale. the laser diode chip is removed from the above package and placed on the eye of an needle for scale.       1.0 Theory of operation A laser diode with the case cut away. The actual laser diode chip is the small black chip at the front; a photodiode at the back is used to control output power. SEM (Scanning Electron Mic..
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Posted: 22/03/2016