Night Vision Optics

Night vision devices (NVD’s) have advanced considerably in recent years and this sophisticated technology is now easily available for anybody interested in outdoor pursuits such as camping, fishing, hunting, astronomy or sailing. Night vision devices work by capturing existing ambient light through the front lens. This light, which is made up of photons goes into a photocathode tube that transforms the photons into electrons. The electrons are then thrown against a phosphorus screen that changes the amplified electrons back into visible light which can be seen through the eyepiece. This image will appear as a clear, green-hued re-creation of the originally observed scene.The main difference between various night vision devices is which type of image intensifier tube is used. A Night Vision Device can be either a 1st, 2nd or 3rd generation:Generation I A GEN 1 unit will amplify the existing light several thousand times to provide an image that is magnified and easily viewed by the night scope’s eyepiece (ocular). These units are the most reasonably priced night vision devices and so provide the greatest value to people seeking night vision capabilities.Generation II GEN 2 devices use a micro-channel plate to achieve lower image distortion as well as higher light amplification characteristics. This extra process allows GEN 2 units to amplify the light many more times than their GEN 1 counterparts, creating a significantly brighter and sharper image.Generation III These devices have gallium arsenide added to the intensifier tube and a special protective film on the micro-channel plate, which increases the life of the tube, thus providing the user with good to excellent low light performance. GEN 3 devices are military standard.For more information and to view a comprehensive range of NVD’s, visit www.sherwoods-photographic.com, a family owned company who specialise in telescopes and binoculars

X-ray astronomy

X-ray astronomy is the study of astronomical objects at X-ray wavelengths. Typically, objects emit X-ray radiation as synchrotron emission (produced by electrons oscillating around magnetic field lines), thermal emission from thin gases above 107 (10 million) kelvins, and thermal emission from thick gases above 107 Kelvin.[33] Since X-rays are absorbed by the Earth's atmosphere, all X-ray observations must be done from high-altitude balloons, rockets, or spacecraft. Notable X-ray sources include X-ray binaries, pulsars, supernova remnants, elliptical galaxies, clusters of galaxies, and active galactic nuclei.[33]
According to NASA's official website, X-rays were first observed and documented in 1895 by Wilhelm Conrad Röntgen, a German scientist who found them quite by accident when experimenting with vacuum tubes. Through a series of experiments, including the infamous X-ray photograph he took of his wife's hand with a wedding ring on it, Röntgen was able to discover the beginning elements of radiation. The "X", in fact, holds its own significance, as it represents Röntgen's inability to identify exactly what type of radiation it was.
Furthermore, according to the website, in some German speaking countries, X-rays are still sometimes referred to as Röntgen rays, in honor of the man who discovered them.

Ultraviolet astronomy

Ultraviolet astronomy is generally used to refer to observations at ultraviolet wavelengths between approximately 100 and 3200 Å (10 to 320 nm).[33] Light at these wavelengths is absorbed by the Earth's atmosphere, so observations at these wavelengths must be performed from the upper atmosphere or from space. Ultraviolet astronomy is best suited to the study of thermal radiation and spectral emission lines from hot blue stars (OB stars) that are very bright in this wave band. This includes the blue stars in other galaxies, which have been the targets of several ultraviolet surveys. Other objects commonly observed in ultraviolet light include planetary nebulae, supernova remnants, and active galactic nuclei.[33] However, as ultraviolet light is easily absorbed by interstellar dust, an appropriate adjustment of ultraviolet measurements is necessary

Optical astronomy

Historically, optical astronomy, also called visible light astronomy, is the oldest form of astronomy.[36] Optical images were originally drawn by hand. In the late 19th century and most of the 20th century, images were made using photographic equipment. Modern images are made using digital detectors, particularly detectors using charge-coupled devices (CCDs). Although visible light itself extends from approximately 4000 Å to 7000 Å (400 nm to 700 nm),[36] the same equipment used at these wavelengths is also used to observe some near-ultraviolet and near-infrared radiation.

Infrared astronomy

Infrared astronomy deals with the detection and analysis of infrared radiation (wavelengths longer than red light). Except at wavelengths close to visible light, infrared radiation is heavily absorbed by the atmosphere, and the atmosphere produces significant infrared emission. Consequently, infrared observatories have to be located in high, dry places or in space. The infrared spectrum is useful for studying objects that are too cold to radiate visible light, such as planets and circumstellar disks. Longer infrared wavelengths can also penetrate clouds of dust that block visible light, allowing observation of young stars in molecular clouds and the cores of galaxies.[34] Some molecules radiate strongly in the infrared. This can be used to study chemistry in space; more specifically it can detect water in comets

Observational astronomy

In astronomy, the main source of information about celestial bodies and other objects is the visible light or more generally electromagnetic radiation.[32] Observational astronomy may be divided according to the observed region of the electromagnetic spectrum. Some parts of the spectrum can be observed from the Earth's surface, while other parts are only observable from either high altitudes or space. Specific information on these subfields is given below.