C-7 Home Page 
C-7 News
Consignment
Library
Products & Services
Product Lines
Order
Search C7.com
|
|||||
|
SHELYAK INSTRUMENTS OVERVIEW"An entirely different way to study the stars, and with some really cool gear!"
Information and advice about spectroscopy for you, and how to select your own Shelyak instrument
The spectrometer (or spectrograph) is a device used to observe or with the aid of a camera or other equipment to record spectra; spectroscopy is the use of a spectrometer to perform chemical analysis of the radiative energy involved in the interactions at the source of that energy. Sometimes equipment can be optimized for specific applications, for example the spectrohelioscope was devised to study the spectrum of the Sun. Shelyak Instruments are well at home in Universities and at government research laboratories. However,
There are many fine articles readily available to those who seek to learn more about spectrographs and spectroscopy, a number of the excellent introductory and instructional articles are being added to our
Right: glass prism demonstration of white light and its dispersion into component colors (28,448 bytes). The range of visible colors of the spectrum span from the upper range of the ultraviolet at about 370nm, continuing up through the blue, green, reds, and into the deep red at about 700nm where the infrared spectrum commences. Spectral lines are produced by the emission of or by the absorption of energy in the form of light. These darker (absorption) or lighter (emission) wavelength spectral lines have a precise location on the spectrum that is caused by electrically charged atoms or a group of atoms (molecule) correlating to specific elements. So the location of that line indicates the element, it’s fingerprint so to speak, while the prominance of that line is an indicator of the abundance of that ion. These indicators of specific elements were first described in 1802 by the English chemist William Hyde Wollaston (1766-1828) whose observations led to the discovery of several elements, substances that are the building blocks of matter, in the Sun. Later the German physicist Joseph von Fraunhofer (1787-1826) too noted these lines, he observed them and carefully measured them thereby identifying some 570 lines; part of his fame to this day derives from having labeled the most prominent lines with the letters A to K known as Fraunhofer Lines, these are shown on the spectrum illustration below:
Above: spectrum spanning from the vacuum ultraviolet (180nm), through visible (~370 to 700nm), and into infrared (above 900nm). This also illustrates several of the better known Fraunhofer lines (C to K). Colors containing only one wavelength are termed a pure or spectral color. You can see in the spectrum shown above that the spectrum does not however contain all the colors that the human eye can distinguish, this is because unsaturated colors such as pink, or purple variations such as magenta are absent for example appear only when combining multiple wavelengths. As science gained a greater understanding of the nature of things then the term spectra has been applied to well beyond the visible and to the entire electromagnetic spectrum. What Do We Do With It? In astronomy, stellar classification includes the characterization of stars based on their chemical composition derived from studying their spectral (or elemental) characteristics. The practice has been extended to the study and classification of nebulae and other celestial bodies. Spectroscopy has helped to identify elements on Earth as well as in space. For example in 1868 English scientist Sir Joseph Norman Lockyer (1836-1920) was conducting studies of the Sun with his 6-¼ inch aperture refractor telescope that he equipped with a spectroscope. He would have observed something like the solar spectrum below: 
In the spectrum of an area near the limb of the Sun he observed a prominent yellow line at 587.49 nm, after eliminating other elements as having produced that line he named the previously unknown element Helium after the Greek Helios. Later during the total solar eclipse of 18 August 1868 the French astronomer Pierre Jules César Janssen (1824-1907) independently noted the same element appearing in the spectrum of a prominence. Lockyer and Janssen were credited as co-discoverers of Helium, that was later isolated on Earth by other scientists. Incidentally, the original 6-¼ telescope lens, was removed from the original home-made optical tube installed into an improved tube assembly in 1871 that remains in use at the
Right: Shelyak LHIRES III Spectrograph employed for solar studies, attached to a TeleVue Optics apochromat telescope (65,921 bytes).
Left: Ceiling lamp with tungsten filament light bulbs as it appears to the naked eye. But slip an economical diffraction grating in line between you and the camera, and WOW! Absorption spectroscopy refers to spectroscopic techniques that measure the absorption of radiation, as a function of frequency or wavelength, due to its interaction with a sample. The sample absorbs energy, i.e., photons, from the radiating field. The intensity of the absorption varies as a function of frequency, and this variation is the absorption spectrum. Absorption spectroscopy is performed across the electromagnetic spectrum. Absorption spectroscopy is employed as an analytical chemistry tool to determine the presence of a particular substance in a sample and, in many cases, to quantify the amount of the substance present. Infrared and ultraviolet-visible spectroscopy are particularly common in analytical applications. Absorption spectroscopy is also employed in studies of molecular and atomic physics, astronomical spectroscopy and remote sensing. There are a wide range of experimental approaches to measuring absorption spectra. The most common arrangement is to direct a generated beam of radiation at a sample and detect the intensity of the radiation that passes through it. The transmitted energy can be used to calculate the absorption. The source, sample arrangement and detection technique vary significantly depending on the frequency range and the purpose of the experiment.
|
|
| ||
|
Contents Copyright 1994-2016 Company Seven, Shelyak Instruments and respective contributors, All Rights Reserved |
What Is It? The word spectrum is derived from the Latin terms specter, meaning “an image or apparition”, and from specere meaning “to observe”. It was in the 17th century, certainly an age of discovery, when the term spectrum was first applied in the field of optics. Sir Issac Newton experimented with optical lenses and mirrors, and it was he who with pair of simple prisms in 1666 first reasoned how sunlight was composed of many colors. He came to define spectrum as the continuous spectrum rainbow of colors which appear when white light is passing through a dispersive glass prism and becomes separated into its component (pure) colors. By 1704 Sir Issac had accumulated enough new knowledge to publish Opticks, that included a detailed study of the dispersion and recombining of colors by prisms among other subjects.
)
)
){kind=link}