Potassium ferrous oxalate, FeK2(C204)2 H20, is a strong reducing agent and is used as a photographic developer.
Photographic telescope was afterwards added, no fewer than 75,000 photographs had been obtained up to the beginning of 1901.
The height of the walls in the various observatories, the height of the collectors, and the distance they project from the wall vary largely, and sometimes electrometer, and they sometimes leave hardly a trace on the photographic paper.
The application of photography to exact astronomy has created the necessity for new forms of apparatus to measure the relative positions of stellar and planetary images on photographic plates, and the relative positions of lines in photographic spectra.
It is practically impossible to work with the sensitive film in contact with the reseau-film, not only because dust particles and contact would injure the silver film, but also because the plate-glass used for the photographic plates is seldom a perfect plane.
The discrepancies produced in this way are, however, very small, if care is taken to minimize the distance between the silver film and the photographic plate and to select a reasonably good piece of glass for the reseau.
The object glass of the micrometer-microscope is placed midway between the plane of the photographic plate and the plane of the micrometer webs.
164) described a measuring-machine by Repsolds, in which the micrometermicroscope tilts in the bearings of the chariot on which it moves, so that it can view either a graduated scale or the photographic plate.
In addition to these we have the photographic plates in F.
A ray of light is directed upon the mirror, and the motion of the latter, due to the varying strengths and direction of the received currents, is made to write the transmitted signals upon a strip of bromide photographic paper about three inches wide.
In the Korn apparatus the light from a Nernst electric lamp is concentrated to a point by means of a lens on the original picture, which is wound on a glass cylinder in the shape of a transparent photographic film.
At the receiving station a cylinder - which revolves synchronously with the transmitting cylinder - is covered with a photographic film or paper, upon a point of which a pencil of light from a Nernst lamp is concentrated.
Aperture evoked the comment in his journal for that year, "There is not now a single person employed or instrument used in the observatory which was there in Mr Pond's time"; and the transformation was completed by the inauguration of spectroscopic work in 1868 and of the photographic registration of sun-spots in 1873.
It is, in fact, admitted that some of the glasses, most useful optically, the dense barium crown glasses, which are so widely used in modern photographic lenses, cannot be produced entirely free either from noticeable colour or from numerous small bubbles, while the chemical nature of these glasses is so sensitive that considerable care is required to protect the surfaces of lenses made from them if serious tarnishing is to be avoided.
The increasing importance of the camera obscura as a photographic instrument makes it desirable to bring together what is known of its early history, which is far more extensive than is usually recognized.
The photographic method appears to have practically failed during recent years, since there has been no brilliant display upon which to test its capacity.
It contains numerous illustrations; maps of the routes of the ancient aqueducts and the city of Rome in the time of Frontinus; a photographic reproduction of the only MS. (the Monte Cassino); several explanatory chapters, and a concise bibliography, in which special reference is made to P. d Tissot, E tude sur la condition des agrimensores (1879).
Great skill is shown in this operation, which achieves perhaps the finest facsimile reproduction of drawings ever known withotit the aid of photographic processes.
Interesting stars are: a Aurigae or Capella (the goat), one of the brightest stars in the heavens, determined by Newall and Campbell to be a spectroscopic binary; [3 Aurigae, a star of the second magnitude also a spectroscopic binary; e Aurigae, an irregularly variable star; and Nova Aurigae, a "new" star discovered by Anderson in 1892, and afterwards found on a photographic plate exposed at Harvard in December 1891.
Many experiments have also been made by the use of photographic plates in order to find the greatest depth to which light penetrates.
Later apparatus, such as Pettersson's bifilar current-meter or his more recent electric-photographic apparatus, and Nansen and Ekman's propeller current-meter, measure both the direction and the velocity at any moderate depth from an anchored vessel.
His experiments, in the same year, on the photographic registration of stellar spectra, marked an innovation of a momentous character.
But the wet collodion process was then the only one available, and its inconveniences were such as to preclude its extensive employment; the real triumphs of photographic astronomy began in 1875 with Huggins's adoption and adaptation of the gelatine dry plate.
Rochester ranks first among the cities of the United States in the manufacture of photographic materials and apparatus and optical instruments.
His earliest work was concerned with improvements in photographic processes; and then, in association with J.
In 1854 he turned his attention to solar physics, and for the purpose of obtaining a daily photographic representation of the state of the solar surface he devised the photo-heliograph, described in his report to the British Association, "On Celestial Photography in England" (1859), and in his Bakerian Lecture (Phil.
A was published in photographic facsimile in 1879-1880.] Codex Ephraemi Syri Rescriptus (Paris Nat.
He especially devoted himself to investigations of the radiation of heat from the sun and its absorption by the earth's atmosphere, and to that end devised various delicate methods and instruments, including his electric compensation pyrheliometer, invented in 1893, and apparatus for obtaining a photographic representation of the infra-red spectrum (1895).
From 1847 to 1862 he was advising astronomer to the headquarters of the army and navy; chairman of the International Astronomical Congress from 1867-1878; acting president of the International Metric Commission in 1872; and president of the International Congress for a Photographic Survey of the Stars in 1887, in which year he was also made a privy councillor.
Had the copies made of ancient writings been mechanical reproductions of the originals, such as the photographic facsimiles of modern times, there would have been little here for textual criticism to do.
The telescope serves to examine the image of the slit and to measure the angular separation of the different slit images; when photographic methods are employed the telescope is replaced by a camera.
Its labors embraced not only Egypt and Nubia (as far as Khartum) but also the Egyptian monuments in Sinai and Syria; its immense harvest of material is of the highest value, the new device of taking paper impressions or squeezes giving Lepsius a great advantage over his predecessors, similar to that which was later conferred by the photographic camera.
The movements of the apparatus, which when complete should consist of two similar pendulums in planes at right angles to each other, are recorded by means of a beam of light, which, after reflection from the mirror or mirrors, passes through a cylindrical lens and is focussed upon a moving surface of photographic paper.
With this arrangement of crossed slits a spot of light impinges on the photographic surface and, when the boom is steady, gives a sharp fine line.
Characteristic, also, is their action on a photographic plate, and the phosphorescence which they occasion when they impinge on zinc sulphide and some other salts.
Suppose a fixed image of the sun to be formed on the collimator slit of this spectroscope, and a photographic plate, with its plane parallel to the plane of the solar image, to be mounted almost in contact with the camera slit.
The eyepiece is removed and the photographic plate (k) placed in position.
By setting the camera slit so as to admit to the photographic plate the light of the denser calcium vapour, which lies at low levels, or that of the rarer vapour at high levels, the phenomena of various superposed regions of the atmosphere can be recorded.
In importance next to visual observation, and in the opinion of some, surpassing it, is the photographic method.
Schumann 2 have shown, however, that with the help of spectroscopes void of air and specially prepared photographic plates, spectra can be registered as far down as lzoo A.
Photographic methods have been employed successfully by Sir W.
Balmer's formula received a striking confirmation when it was found to include the ultra-violet lines which were discovered by Sir William Huggins' in the photographic spectra of stars.