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Vidicon tube 2 ⁄ 3 inch (17 mm) in diameter A display of numerous video camera tubes from the 1930s and 1940s, photographed in 1954, with iconoscope inventor Vladimir K. Zworykin. Video camera tubes are devices based on the cathode-ray tube that were used in television cameras to capture television images, prior to the introduction of charge ...
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Earth's rotation axis moves with respect to the fixed stars (inertial space); the components of this motion are precession and nutation. It also moves with respect to Earth's crust; this is called polar motion. Precession is a rotation of Earth's rotation axis, caused primarily by external torques from the gravity of the Sun, Moon and other bodies.
Two iconoscope tubes. The type 1849 (top) was the common tube used in studio television cameras. The camera's lens focused the image through the tube's transparent "window" (right) and onto the dark rectangular "target" surface visible inside. The type 1847 (bottom) was a smaller version.
Due to the very slow pole motion of the Earth, the Celestial Ephemeris Pole (CEP, or celestial pole) does not stay still on the surface of the Earth.The Celestial Ephemeris Pole is calculated from observation data, and is averaged, so it differs from the instantaneous rotation axis by quasi-diurnal terms, which are as small as under 0.01" (see [6]).
But the magnetic focusing for video camera tubes invented by Farnsworth in 1928 --via a long focusing coil placed along the tube-- survived the image orthicon era and it was a main ingredient in the vidicon and similar tubes; see the vidicon's diagram in the article.
The camera section held the lens and camera tube pre-amplifiers and other necessary electronics, and was connected to a large diameter multicore cable to the remainder of the camera electronics, usually mounted in a separate room in the studio, or a remote truck. The camera head could not generate a video picture signal on its own.
The aims of the designers of the camera were, firstly, to produce a camera that was more tolerant to mis-registration and, secondly, to achieve a lighter camera by using smaller vidicon tubes to replace some of the large heavy IO tubes. The camera had an image orthicon tube for the luminance channel and three vidicon tubes for the colour ...